Q.A bill dated 5th March 2024 is made payable 60 days after date. Calculate its due date.

When a bill's term is stated in days, every day is counted from (but excluding) the date of the bill, and three days of grace are added at the end.

Step 1 — Count 60 days from 5th March, excluding the date of the bill. March (after the 5th) contributes 26 days (6th to 31st), taking the running count to 26 of the 60 days. April, a full 30-day month, takes the running total to 56 days (26 + 30). The remaining 60 − 56 = 4 days fall in May, landing on the 4th of May 2024 as the nominal due date (the 60th day).

Step 2 — Add days of grace. 4th May + 3 days = 7th May 2024.

Verification (independent cross-check using day-of-year numbers, 2024 being a leap year): 5th March is the 65th day of the year (31 days of January + 29 days of February + 5). Day 65 + 60 = day 125. January, February, March and April together account for 31 + 29 + 31 + 30 = 121 days, so day 125 is the (125 − 121) = 4th day of May — i.e. 4th May, exactly matching the first method. Adding 3 days of grace again gives 7th May 2024.

Including the date of the bill itself while counting the days (which overstates the count by one day); miscounting the number of days in March or April; and forgetting the three days of grace at the end of the day-count.