Period that begins with a day of pranks: Abbr.

APR

This three-letter month follows the spring equinox and is known for showers that bring May flowers.

This clue refers to April, which starts with April Fools' Day—a well-known day for playing pranks. The abbreviation "APR" is commonly used for April in calendars and schedules. The wordplay is straightforward: the "period" is the month, and the "day of pranks" narrows it down to April.