Add or Subtract Custom Time Intervals
Worked Example: Accumulating Project Hours
Suppose you have three project work blocks: 3 hours 45 minutes, 4 hours 30 minutes, and 2 hours 55 minutes:
- Sum the hours = 3 + 4 + 2 = 9 hours
- Sum the minutes = 45 + 30 + 55 = 130 minutes
- Convert extra minutes to hours = 130 minutes = 2 hours and 10 minutes
- Grand total duration = 9 hours + 2 hours 10 minutes = 11 hours 10 minutes
The time calculator handles this rollover math cleanly, returning 11 hours 10 minutes.
Time Computations and Standardization
Because time is non-decimal (based on sexagesimal or base-60 numbering systems), summing or subtracting time units requires modulo conversion. Standard hours-to-decimals arithmetic utilizes division by 60 for minutes, and 3600 for seconds.
For example, if you accumulate a shift roster summing up to exactly **8 hours and 45 minutes**, the decimal equivalent is:
Frequently Asked Questions
If the shift End Time is earlier than the Start Time, the roster engine assumes the shift crosses midnight. It adds 24 hours to the end time before performing subtraction, resulting in precise duration logs (e.g. 10:00 PM to 6:00 AM logs exactly 8 hours).
Standard accounting packages require decimal formats to compute aggregate wages (e.g. multiplying Hourly Rate by 8.75 hours, rather than multiplying by 8:45, which would fail mathematically).