⏰ Adding, Subtracting and Converting Time Values

2 hours 45 minutes plus 1 hour 30 minutes isn't 3 hours 75 minutes — it's 4 hours 15 minutes. Time math trips people up because it doesn't work in base 10 like regular arithmetic; it works in base 60 for minutes and seconds.

Why Time Math Isn't Regular Addition

Adding two durations means adding hours to hours and minutes to minutes separately, then "carrying over" any time the minutes total reaches 60 — exactly the way you'd carry a 1 when adding numbers that sum past 9, just with a threshold of 60 instead of 10.

Converting Between Units

A common mistake is treating the decimal portion of an hour as if it were minutes directly — 2.5 hours is 2 hours 30 minutes, not 2 hours 50 minutes, because the ".5" means half of 60 minutes, not 50 out of 100.

Calculating Elapsed Time

Given a start and end clock time, elapsed time is the end time minus the start time — straightforward until the times cross midnight, at which point the calculation needs to add 24 hours before subtracting, or it'll produce a negative or nonsensical result.

Time Tracking Across Multiple Entries

Adding up several separate time entries (like a timesheet with multiple tasks) is the same carry-over addition repeated across every entry — small individual entries can add up to unexpected totals once all the minute carry-overs are accounted for.

Step-by-Step: Work With Time Values

1. To convert: enter a value and choose the units to convert between
2. To calculate elapsed time: enter a start and end time
3. To add multiple entries: enter each hours/minutes/seconds value and get the running total