A “perfect” month 👌

… is one that is only 28 days with each weekday slotting into exactly four weeks.

In the 21st century (2001–2100), February has exactly 28 days and starts on a Sunday in the following years:

• 2009
• 2015
• 2026
• 2037
• 2043
• 2054
• 2065
• 2071
• 2082
• 2093
• 2099

Frequency and Rules

This specific calendar alignment—known as a perfect month—occurs only in common years (non-leap years). It follows a repeating cycle of 6, then 6 and 11 years (e.g., 2015 + 11 = 2026; 2026 + 11 = 2037).

Leap Year Exception: Years such as 2004, 2032, 2060, and 2088 also have February 1st falling on a Sunday, but because they are leap years, February has 29 days rather than 28.

End of Century: The year 2100 is technically a common year (28 days in February) because centurial years must be divisible by 400 to be leap years. However, February 1, 2100, will fall on a Monday, not a Sunday.