WordPress Locale, Dates & Numbers

WP's date/time API has TWO eras: pre-5.3 (offset-summed timestamps, date_i18n, current_time('timestamp') — quirky, error-prone) and 5.3+ (true UTC timestamps, DateTimeZone objects, wp_date, current_datetime). Most plugins still write pre-5.3 code because that's what AI training data is full of. This skill is the modern recipe.

When to use this skill

Trigger when ANY of the following is true:

• A plugin stores, queries, or displays dates / times — scheduled tasks, expiry dates, audit timestamps, log entries, "X minutes ago" labels, REST date fields.
• Code references wp_date, current_datetime, current_time, date_i18n, wp_timezone, wp_timezone_string, get_gmt_from_date, get_date_from_gmt, mysql2date, mysql_to_rfc3339, iso8601_to_datetime, number_format_i18n.
• Code calls time(), date(), strtotime() directly for site-display dates without considering timezone.
• The user reports: "wrong timezone on schedule emails", "WP-Admin shows EST but database has UTC", "Friday in Europe shows as Thursday in REST".

The mental model — timestamps are UTC, formatting is local

Since WP 5.3, the rule is: