Day of the Week: 5 Mistakes to Avoid
Tells you which weekday any date falls on. The maths is not complicated, but a handful of errors come up again and again in this and related date & time calculations. Here is what to watch for.
Many Singapore rules are expressed in days: notice periods, leave entitlements, stamp duty deadlines and probation periods. Whether the count includes the start or end date, and whether weekends count, changes the answer.
Age is calculated in completed years, months and days. Someone born on 29 February is usually treated as turning a year older on 28 February or 1 March in non-leap years, depending on the rule being applied.
1. Mixing date formats
5/10 can mean 5 October or 10 May depending on the convention.
2. Subtracting times in decimal
9:45 minus 8:30 is 1 h 15 min, not 1.15 hours.
3. Forgetting public holidays
Working-day counts usually need holidays removed.
4. Assuming every month has 30 days
Month lengths vary from 28 to 31 days.
5. Not deciding whether to include the end date
Counting inclusively adds one day.
The correct method
Based on the Gregorian calendar.
For example, with these inputs:
- Date: 9 Aug 1965
the calculator returns:
- Day: Monday
Related calculations
- Age Calculator: Calculates exact age in years, months and days.
- Days Between Dates Calculator: Counts days between two dates.
- Add Days to a Date Calculator: Finds the date a number of days after another date.
- Subtract Days from a Date Calculator: Finds the date a number of days before another date.
The Day of the Week Calculator applies the formula consistently, so it is a quick way to double-check your own working.
Run your own numbers: Day of the Week Calculator