ICS Calendar

How do I find my calendar’s ICS feed URL?

Different calendar systems have different ways to obtain the feed URL. You may need to consult your calendar software’s documentation for assistance. Find instructions for commonly used calendars below.

You will also need to make sure that your calendar is public. Private calendars cannot be accessed by this plugin.

Documentation quick links:

• Google Calendar
• Microsoft Office 365
• Apple iCloud

How do I insert a calendar into my page?

Use this shortcode, inserting your ICS feed URL between the quotation marks:

[ics_calendar url=""]

Be sure you are using the iCalendar subscription (ICS) URL (i.e. for importing into a calendar program), not the URL for viewing a calendar in a web browser. To test if you have the correct URL, paste it directly into your browser address bar. It should download an .ics file, not display the calendar in the browser.

Can I combine multiple calendars?

Yes! You can combine multiple calendars by including more than one feed URL in the url parameter. Separate the calendar URLs with one space or a pipe | character. Do not include any other delimiter characters, as they will be interpreted as part of the URL.

Why isn’t my calendar loading?

This may be due to your server’s configuration. This plugin requires either the PHP cURL extensions, or the allow_url_fopen PHP setting to be turned on. Check your PHP configuration or your server administrator if you think this may be the issue. You can also use the ICS Feed URL Tester utility on the ICS Calendar admin page to check if your server is able to connect to the calendar source.

Why isn’t my calendar updating?

For performance, this plugin uses WordPress transients to store retrieved calendar data for one hour between requests to the calendar source server. If you have updated events that are not showing up in your page, visit the ICS Calendar page in your site admin and click the Clear Cached Calendar Data button.

Third-party caching plugins may interfere with ICS Calendar’s feed syncing. ICS Calendar uses AJAX to work around most caching conflicts, but your caching plugin may require you to add the wp-admin/admin-ajax.php path to its list of exclusions in order for AJAX to function properly.

Why are event times an hour off after Daylight Saving Time begins?

PHP has two different ways of defining timezones: as a number of hours offset from GMT/UTC (e.g. “UTC-5”), or as a continent/city combination (e.g. “America/Chicago”). Timezones using UTC offsets do not handle Daylight Saving Time correctly (as noted in the PHP documentation). Please check your WordPress timezone settings (Settings > General > Timezone). If it is set to a UTC offset, change it to the city closest to your location, in the same timezone. You can also set the timezone within the shortcode using the tz parameter. (Again, be sure to use a named region/city timezone, not a UTC offset.)

Additional documentation and support

Our User Guide includes extensive documentation of all features of the plugin, is frequently updated, and is translated into all languages supported by the plugin.

Feature requests

The paid ICS Calendar Pro add-on includes additional layout options, tools for customizing the calendar’s appearance more easily than directly editing CSS, an improved insertion tool, and more. We are also constantly adding new features and refinements to both the free and paid versions. If you have suggestions for features you’d like to see or any other additional input, please let us know by following the support link on the admin page or in the WordPress support forums! The base plugin will always be free to use.

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12.1.3.2 – 2026.09.03

• Miscellaneous:
  • Fixed “Warning: Undefined variable $ics_data” error on views that use early rendering.
  • Bumped ‘tested up to’ to 7.1.

12.1.3.1 – 2026.08.04

• Week view:
  • Corrected a long-standing CSS bug that had no noticeable effect until the changes in 12.1.2 were introduced.

12.1.3 – 2026.07.28

• Basic view:
  • Fixed a bug that prevented toggle from working when user clicks on an event title. (Clicking the date or time worked, but the title itself did not.)
• List and Basic views:
  • Fixed pagination error when “today” has multiple pages’ worth of events.
• Miscellaneous:
  • Added new date-specific CSS class to events.
  • Resolved conflicting z-index values for event hover.

12.1.2 – 2026.07.14

• Week view:
  • Fixed issue that prevented events from displaying when displaying the current week only or limiting the display to fewer than 8 days.
• CSS:
  • Changed z-index on event hover to avoid conflict with Modern Events Calendar plugin.
• Miscellaneous:
  • Modified R34ICS::parse_attach_array() method to support returning an array in addition to the default string output option.

12.1.1.1 – 2026.07.01

• AJAX:
  • Adjusted minimum refresh time from 5 minutes to 2 minutes, and added a 10-second delay, to account for any lag in clearing the cache. (Actual refresh rate is based on the Transient (cache) expiration setting.)
• Print:
  • Added restrictions on allowed HTML attributes passed into print wrapper.

12.1.1 – 2026.06.26

• Admin:
  • Fixed issue of a large number of irrelevant, version-related admin notices appearing on initial installation.
  • Modified r34ics_admin_full_access() function, adding the $multisite_check parameter. This allows for conditionally checking for Multisite Super Admin access. Prior to this change, in a Multisite configuration, only network Super Admins could access ICS Calendar settings. All settings are site-specific, so site-specific Administrators should be allowed to access them. The conditional retains the ability to check for Super Admin access if needed. (Presently this is only needed for the License tab in the Pro version.)
• Appearance settings:
  • Added “Give ICS Calendar credit” option. (This is turned OFF by default.) Adds a small “Powered by ICS Calendar” credit link below each calendar. Thank you for your support!
• Shortcode parameters:
  • Added eventdescdateformat parameter to allow different formatting for dates in the event description hover box/lightbox than in the main calendar view. If omitted, will fall back to format value or default for the view.
• Miscellaneous:
  • Added r34ics_display_calendar_before_render_template and r34ics_display_calendar_hooks_render_template on early render.
• i18n:
  • Updated translation strings.

12.1.0 – 2026.06.20

• Script loading:
  • Re-introduced conditional enqueuing of static assets (JavaScript and CSS files), which had been removed in an earlier update due to inconsistent behavior. This new method has been tested against the 40 most popular themes in the repository and appears to work reliably in all cases.
  • Added r34ics_enqueue_conditional_scripts action to R34ICS::enqueue_scripts() method, to provide a way for view-specific scripts to still be enqueued when the remainder of the method is being bypassed because the general scripts have already been enqueued.
  • Modified script loading in print.php template to account for the above changes.

12.0.10 – 2026.06.18

• Event descriptions: Added eventdesclinkfix shortcode parameter. Changed r34ics_maybe_make_clickable() function so that, when eventdesclinkfix is used, it will return the text string as-is if it contains any HTML. The assumption here is that descriptions that contain HTML will already have any URLs wrapped in the requisite a tags.

12.0.9.2 – 2026.06.07

• Changed id attribute on AJAX container (appended -ajax) so it isn’t redundant with the id of the calendar itself after loading.

Note: Due the fact that its single change would serve no useful purpose on its own, version 12.0.9.1 was not released in the public WordPress repository, but was included in the ICS Calendar Pro 6.1.10 update.

12.0.9.1 – 2026.06.02

• Removed auto-redirect to settings page on activation.

12.0.9 – 2026.06.02

• Security:
  • Added extra validation for htmltag* shortcode parameters.
• Compatibility:
  • Removed backwards compatibility for WordPress 4.9 (including removal of compatibility.php file, which replicated newer core WordPress functions required by ICS Calendar). Minimum required WordPress version is now 5.3.

= 12.0.8.6 – 2026.05.29

• Fixed bug that caused “Welcome to version 12.0” message to reappear with each update.
• Fixed potential fatal error with debug mode on AJAX loading.
• Modified logic to prevent auto-redirect to ICS Calendar admin page on update/activation, so it will only run on the first activation after installation.

12.0.8.5 – 2026.05.27

• Added support for custom ICS Calendar properties in the feed, using the X-R34ICS- prefix.
• Changed default value for SEQUENCE from an empty string to 0 when parsing events from the feed.
• Updated admin notice handling, including making UTC timezone notice non-dismissible.

12.0.8.4 – 2026.05.19

• Added a safeguard in r34ics_get_vtimezone() to prevent a fatal error if the site does not have a valid region/city name timezone set.
• Modified r34ics_filter_the_content() (used by the R34ICS::event_description_html() method to prepare event description HTML output) to address a situation where the ICS feed includes an event description containing HTML that has been truncated in the middle of a tag. Previously, this would cause an HTML syntax error that would prevent the rest of the page from rendering properly, starting at the point of the error. Added a simple check for a matching number of greater-than and less-than symbols in the content. (This is not full HTML validation, but it addresses the most egregious scenario that breaks rendering.) If the function detects a mismatch, all HTML is stripped from the output.

12.0.8.3 – 2026.05.15

• Introduced r34icsymd parameter to function similarly to r34icsym but including the date along with the year and month. This is part of an ongoing process of updating how r34icsym functions for loading calendar pages with an arbitrary date displayed. Presently this is used exclusively by ICS Calendar Pro Full view.
• Updated tags for Plugin Directory.

12.0.8.2 – 2026.05.11

• Plugin conflicts:
  • Added r34ics_resolve_conflicts action to allow for extensible conflict resolution.
  • Replaced experimental workarounds for conflict with Permalink Manager and with code supplied by the developer of that plugin.
• Shortcode parameters:
  • Continued development of enhanced capabilities for r34icsym shortcode parameter. This is mainly used by Full view in ICS Calendar Pro at present, but it will be used to refactor how this query string variable is used to dynamically request a specific date range in all views in a future update.
• Miscellaneous:
  • Minor code refactoring.

12.0.8.1 – 2026.05.08

• Print Button:
  • Changed CSS margin and max-width to allow for 1 cm margin on paper.
  • Fixed “PHP Deprecated: preg_replace(): Passing null to parameter #3” notice relating to use of wp_kses_post() function.

12.0.8 – 2026.05.05

• Updated ua parameter to support a value of append. Set ua="true" to replace ICS Calendar’s custom User Agent string with a “real” web browser UA string. Set ua="append" to append a real web browser UA string to the default ICS Calendar UA string. You can also enter custom text as the value for ua and that exact string will be sent as the UA string with requests. Note: This parameter is intended for use only when source calendars reject requests with the default UA string.
• Additional changes to template_redirect handling to resolve a conflict with the Permalink Manager plugin. (Expands upon changes introduced in 12.0.7.1.)

12.0.7.1 – 2026.04.29

• Added r34ics_get_vtimezone() function for generating iCalendar VTIMEZONE data including Daylight Saving Time start/end rules. Intended to be used by functions and methods that output new .ics files.
• Changed priority for call to template_redirect hook (used for individual event .ics downloads and printing calendars) to resolve a conflict with the Permalink Manager plugin.
• Updated individual event download .ics format to include VTIMEZONE and remove FREEBUSY, to resolve issues importing events into Google Calendar.

12.0.7 – 2026.04.27

• Admin:
  • Added two new settings (under Loading on the ICS Calendar Settings page): Increase time limit when rendering calendars and Increase request timeout when rendering calendars. If your calendars are intermittently failing to load due to time limits, adjusting these settings may resolve the issue. Note that long loading times may indicate connectivity problems between your web server and the source calendar server, or may be the result of excessively large amounts of calendar data. In some cases, you may need to purge old events from your source calendar.
• Feed loading:
  • Modified conditional for transient caching of feeds. Previously it would cache any non-empty response. Now it caches only if the response body begins with BEGIN:VCALENDAR (that is, it’s a valid ICS feed).
• i18n:
  • Updated translation strings.

12.0.6 – 2026.04.01

• Admin:
  • Minor CSS adjustments for WP 7.0 interface changes.
• Month view:
  • Fixed bug in mobile view that would cause the date grid for past months to display incorrectly when nomobile was set.
• Week view:
  • Fixed bug in mobile view that would cause the current week to reappear on scroll, after selecting a different week, in mobile Safari. This issue was specifically an error in the logic of a function that runs on resize, but was exacerbated by the fact that mobile Safari changes the window size on scroll, triggering a resize event.
• Miscellaneous:
  • Bumped PHP requirement to 7.4. (8.0 or later is strongly recommended.)
  • Bumped ‘tested up to’ to 7.0.
  • Updated readme.txt content.
• Vendors:
  • ics-parser: Merged v. 3.5.1 changes into customized version of library.

12.0.5.2 – 2026.03.23

• AJAX:
  • Fixed bug that would cause the next upcoming event to be omitted in List and Basic views, when running PHP 7.4 or earlier.
• Miscellaneous:
  • Began process of refactoring r34ics_init() JavaScript function to address issues when multiple calendars are displayed on the same page. Some logic in this function must run for every calendar, and some of it should only run once per page. The logic that should only run once per page is being moved to a separate r34ics_init_once() function.

12.0.5.1 – 2026.03.11

• Basic view:
  • Fixed feed color coding regression bug introduced in 12.0.0.

12.0.5 – 2026.03.09

• Admin:
  • Added check to only display the initial Quick Start Guide alert if there are no saved calendar feed URLs.
• Functions:
  • Modified r34ics_maybe_make_clickable() to fix regression in converting raw image URLs into img tags; added support for WebP image URLs.
• i18n:
  • Added Icelandic.

12.0.4.2 – 2026.02.27

• Miscellaneous:
  • Modified recursion conditional in R34ICS::_url_get_contents() method to only check for specific text strings in the response when the response code is not 200. This should resolve possible erroneous redirections that occur if the text strings being checked appear in the ICS feed response content itself.
• i18n:
  • Reworked r34ics_i18n_symlinks() to delete old translation files before copying or symlinking new file, to ensure changes are picked up.
  • Updated translation strings.

12.0.4.1 – 2026.02.07

• Miscellaneous:
  • Reverted the redirection change introduced in 12.0.4, as it seems to be breaking the custom redirection logic ICS Calendar already included. In the rare cases where a feed does need redirection to be set to something other than 0, this can be done with custom PHP using the r34ics_url_get_contents_request_args filter.
• i18n:
  • Added workaround logic for edge case with Loco Translate conflict fix (introduced in 12.0.3), for servers where the PHP symlink() function is not available. The plugin now checks for symlink(), falls back to copy() if needed, and if both fail, it displays an admin notice addressing the conflict with Loco Translate.
  • Updated translation strings.

12.0.4 – 2026.02.02

• Print Button:
  • Added logic to print the currently selected month or week in the print view. Previously, printing would revert to the initial month or week selection.
  • Several CSS modifications, including adjusting text size for list-type views vs. table-type views, and flattening list/basic pagination (all “pages” shown in print output).
  • Restored general print CSS media queries; changes for the print button introduced in v. 11.6.0 work only with the print button, not when printing the full page with the browser’s default printing.
• Miscellaneous:
  • Changed redirection value in R34ICS::_url_get_contents() method from 0 to 5. May resolve some feed loading issues when the source returns an HTTP 302 redirect.
  • Refactored CSS.

12.0.3.1 – 2026.01.21

• Modified AJAX conditional in R34ICS::shortcode(), changed in 12.0.3, to handle undefined $args['ajax']. (Probably unnecessary since it’s explicitly defined above, but best practice since there’s a filter that can modify the contents of $args.)
• Tweaked logic in r34ics_is_html() to resolve false negatives.
• Updated new inline image logic in r34ics_maybe_make_clickable() to only run if there is no detected HTML in the string. In some instances the code was converting images that were already in an img tag. (The assumption here will be that if the string contains any HTML, the image will already be in an img tag if that’s the intention.

12.0.3 – 2026.01.19

• AJAX:
  • Made logic for determining whether or not to load the calendar via AJAX more explicit, to resolve an issue that was occurring in certain highly optimized setups involving caching and preloading (e.g. WP Rocket).
• Block Editor:
  • Modified r34ics_is_block_editor() to more effectively limit the conditional check for REST_REQUEST constant.
• Event downloads:
  • Fixed a bug that was causing incorrect event information to be downloaded under certain conditions, apparently affecting mainly Microsoft calendars. According to the iCalendar spec the event UID property is supposed to be persistent, but in some cases (possibly pertaining to modified instances of recurring events) Microsoft calendars assign the same event a new UID each time the feed is reloaded. (There was also a bug in the plugin’s logic that was causing the wrong event’s data to get inserted into the download when this UID mismatch occurred, rather than just failing altogether.) This update resolves the mismatched data bug, as well as adding fallback logic to match events by title, start date/time and end date/time when no UID match is found in the feed.
• Performance:
  • Added r34ics_display_calendar_force_reload filter to allow bypassing the new rate limit related restrictions added in 12.0.0. Please do not use this filter unless you understand the performance impact it may have. By default, ICS Calendar intentionally throttles how frequently requests are made to the source calendar. This is done both to improve your site performance and to avoid hitting source calendar providers’ rate limits, which can result in HTTP 429 errors and failure to load your calendar. (In some extreme cases, providers may rate limit entire networks.) If you have any questions about whether or not it is appropriate to use this filter with your site, please contact support before proceeding.
• Plugin conflicts:
  • Worked around conflict with Loco Translate plugin by creating symlinks to ICS Calendar’s general language translation files with locale-specific names in the WP_LANG_DIR path when Loco Translate is active. (Normally, the general language files self-contained within ICS Calendar load directly, but Loco Translate overrides this functionality.)
• Miscellaneous:
  • Refactored instances of directly checking the active_plugins core option to use the is_plugin_active() function instead.

12.0.2 – 2026.01.16

• Event descriptions:
  • Modified r34ics_maybe_make_clickable() function to convert raw image file URLs in event descriptions directly into HTML img tags, instead of clickable links. May be a useful workaround for including images in event descriptions for sources like Google Calendar and Microsoft 365, which do not make files directly accessible. _Note: The URL must be a direct URL to a publicly accessible image file, with a standard image extension (supported extensions: .apng, .avif, .gif, .jpg, .jpeg, .png, .svg). Using a URL that links to Google Drive, OneDrive, iCloud, Dropbox, etc. will not work, because those are permission-restricted “wrapper” page URLs, not the direct URLs of the files themselves.
• Miscellaneous:
  • Added fallback values for possibly undefined keys in R34ICS::display_calendar_date_range() method. (There is no evidence that this was actually an issue but it’s best practice and may help with resolving a date range issue affecting certain users.)
  • Added SVG tag support to r34ics_color_key_allowed() function to allow SVG images to be included in the legend (color key). Mainly used by ICS Calendar Pro for the Subscribe button.
  • Changed legend to use --r34ics--element--events--color text color (the same as events).
  • Other minor CSS tweaks.
  • Added phpcs:ignore WordPress.WP.I18n.MissingTranslatorsComment to a translation string in admin page to pass Plugin Check test.

12.0.1 – 2026.01.06

• Admin: Updated Pro version promo block.
• i18n: Updated translation strings.

12.0.0.1 – 2026.01.05

• Added conditional to avoid a potential fatal error in the r34ics_scrub_duplicate_uids() function. (This function runs only when the fixredundantuids parameter is set.)
• Added $force_reload parameter to R34ICS::display_calendar() method.
• Removed CSS that causes event time and title not to appear in description hover box on mobile.

12.0.0 – 2025.12.29

• Admin:
  • Added Allow access to these ports setting to allow defining custom HTTP ports for feed requests. Useful if your source calendar server uses a custom port number and you are having trouble retrieving the feeds.
  • Added Pause Calendars button (under Utilities) to temporarily shut off all ICS Calendar output on front-end pages.
  • Added Register Customizer setting to enable the Customizer on Block Themes, for users who may want to add their own custom CSS without editing their theme files. (Note: The WordPress core team is phasing out support for the Customizer so this may eventually stop working.)
  • Added r34ics_admin_full_access() function for Multisite-aware restriction of access to Administrator-only features, and r34ics_admin_access() function for configurable level of access to all admin features.
  • Changed default access level from Author to Editor; added Minimum access role setting to make this configurable.
  • Fixed issue with settings page loading scrolled partially after saving changes.
  • Fixed possible false negatives on valid feed URL status with ICS Feed URL Tester utility.
  • Refactored admin page template files.
  • Removed Also reset all ICS Calendar settings checkbox on Clear Cached Calendar Data utility for non-Administrators.
  • Removed System Report tab for non-Administrators, since only Administrators can access the System Report.
  • Various design and layout refinements on Settings and Help screens.
• AJAX:
  • Removed Always use AJAX to render calendars option; AJAX is now automatic unless ajax="false" is explicitly added to the shortcode.
• Color:
  • Deprecated whitetext shortcode parameter. Use Dark Mode setting on ICS Calendar Settings page instead, or darkmode="true" on individual shortcodes.
  • Fixed some inconsistencies with text colors.
  • Lightened background tints of color-coded feed events for better text contrast.
• CSS:
  • Extensively restructured CSS for greater efficiency (especially making use of the :is() pseudo-element).
  • Moved most color specifications to CSS variables for easier customization.
  • Updated handling of word-break and hyphens to eliminate vendor prefixes and undesirable break-all setting.
• Developer:
  • Added r34ics_url_get_contents_request_args filter.
  • Added support for overriding default calendar templates by creating an ics-calendar folder within your theme or child theme, and placing appropriately named replacement files (e.g. calendar-month.php) in that folder. Developers who wish to override templates are encouraged to copy the existing template to use as a starting point.
• Event Downloads (eventdl):
  • Modified handling of recurring events in the event download link, so the download now contains only the single selected instance of the event, rather than the full recurrence set.
• Month/Week Views:
  • combinemultiday now defaults to true.
• Performance:
  • Added r34ics_rate_limit_check() function to identify situations where calendars may be hitting rate limits, and display an admin notice with recommended steps to remedy the situation.
  • Added conditional before r34ics_url_uniqid_update() calls in R34ICS::_url_get_contents() and R34ICS::_url_get_contents_legacy(), to run it only if we’ve verified the URL returns iCalendar formatted data. Also added r34ics_url_uniqid_delete() to delete individual feed URLs from the list.
  • Due to observed issues with some sites using reload in ways that exceed request rate limits, causing providers like Google Calendar to put temporary blocks on IP ranges, the reload option is now forced to a minimum value of 120 (2 minutes), unless debug is also set to 2 or higher. The reload option is intended for troubleshooting only. If your calendar updates more frequently than once per hour, the best option is to change the Transient (cache) expiration setting to a lower value. Recommended value: 300 (5 minutes).
• Plugin Conflicts:
  • Elementor: Added jQuery code to re-run ICS Calendar’s initialization script when switching Elementor tabs. Resolves an issue where some calendars may not render properly in tabs.
• Utilities:
  • Added “Also clear all saved ICS feed URLs” option to ICS Calendar Data Cache utility. This allows for purging the list of previously retrieved feed URLs in addition to cached transient data. (Previously the only way to purge the list of feed URLs was to use the “Reset all ICS Calendar settings” option.)
  • Updated status message output and fixed false negative bug with ICS Feed URL Tester utility.
• Miscellaneous:
  • Added r34ics_reset_non_empty_defaults() function and associated filter for managing setting/resetting initial non-empty option values.
  • Added dynamic cookie handling when interacting with source servers that send cookies. May resolve an issue for Google Calendar users in Europe.
  • Changed most saved options to autoload = false.
  • Removed r34ics_curl_cookie_path() function and deprecated code that used it.
  • Refactored several functions and addressed various minor bugs.
  • Removed disused asset files.
  • Removed r34ics_curl_cookie_path() function and deprecated code that used it.
  • Renamed JS and CSS asset files to include -pro in the filenames. (To prevent confusion during development.)
  • Updated and reformatted System Report output.
  • Updated System Report formatting and added new settings fields.
  • Updated user agent string logic (v. 11.5.15.1) to include Google Calendar, and updated the base UA string.
  • Various other minor code refactoring throughout the plugin to address inefficiencies, improve organization, and resolve some PHP notices and warnings.
• a11y:
  • Added tab support for help hover boxes on admin pages.
• i18n:
  • Added new translations: Romanian, Serbian, Slovak, Turkish and Ukrainian.
  • Revised all translation strings for all languages. Please note: By necessity we are using machine translations. (Most strings are translated by DeepL; a few that produced errors with DeepL are cross-referenced with Google Translate.) If you find any translation errors, please let us know at the link below.
  • Streamlined language files to one default file per language, rather than separate files for each locale. Note: This will make translations available to many more locations, rather than defaulting to U.S. English if a file for a specific language and locale were not previously present. However, the new translations may be slightly less accurate for specific locales that previously had a dedicated file.
• Vendors:
  • Incorporated recent ics-parser changes into our customized version.

If you identify any translation issues, please use our Translation Suggestions form to contact us.

Full Changelog

Changelog truncated here due to WordPress repository requirements. Please see changelog.txt for older logs.