Weekday Checker is a free Chrome add-on designed to enhance your email communication by verifying the accuracy of dates and corresponding days of the week. This tool automatically monitors input fields for phrases that include both a day of the week and a date. When it detects a mismatch—such as stating 'Tuesday, Jan 21' when Jan 21 is actually a Wednesday—it promptly alerts users with a popup notification. This feature helps prevent confusion in professional correspondence and ensures clarity in scheduling.

The add-on is user-friendly and operates seamlessly in the background. Once it alerts a user about a specific date and day mismatch, it will not issue another alert for that phrase unless the text is removed and re-entered. This design allows users to easily correct their mistakes or confirm that the mismatch was intentional, providing a simple yet effective solution for maintaining accuracy in date-related communications.