Day and Date Calculations — Revision Notes

⚡ 30-Second Revision

Elapsed days, then remainder seven. Gregorian leap year: divisible by 4, except centuries unless divisible by 400. Check whether the interval includes 29 February. Move backward for earlier dates.

2-Minute Revision

2000 is leap; 1900 and 2100 are common. January plus February 2024 gives 60 elapsed days to 1 March, a four-weekday shift. From 10 April to 5 May is 25 days, not 26. March 2023–March 2024 includes leap day; March 2024–March 2025 does not. A 400-year Gregorian cycle repeats the calendar; a 28-year rule has century exceptions.

5-Minute Revision

Recalculate the three worked examples using two different interval partitions. Check Monday 1 January 2024 to Friday 1 March; Thursday 10 April to Monday 5 May; and Saturday 20 June back to Friday 5 June. Explain the exact source of a one-day error in each nearby wrong answer.

Vyyuha Quick Recall

Calendar, interval, leap day, remainder, direction.