The number of days in a month varies depending on the month:

• January : 31 days
• February : 28 days (29 days in a leap year)
• March : 31 days
• April : 30 days
• May : 31 days
• June : 30 days
• July : 31 days
• August : 31 days
• September : 30 days
• October : 31 days
• November : 30 days
• December : 31 days

If you want, I can also explain how to remember these or provide details about leap years!