Step-by-step
Xchart calculates anesthesia time by counting the number of whole minutes between the recorded Anesthesia Start and Anesthesia End times.
1. Record the timestamps
Two timestamps are used:
Anesthesia Start
Anesthesia End
These times are recorded with full precision (including seconds and milliseconds).
2. Convert each timestamp to a minute
Before calculating the duration, Xchart drops the seconds and milliseconds from both timestamps.
Example:
Actual Time | Used for Calculation |
3:30:00 | 3:30 |
3:30:59 | 3:30 |
4:00:54 | 4:00 |
3. Calculate the difference
Xchart subtracts the start minute from the end minute.
Example:
Start: 3:30:00
End: 4:00:54
Calculation:
4:00 − 3:30 = 30 minutes
Why seconds are ignored
This matches how time is normally displayed on digital clocks and anesthesia records.
For example:
Start: 3:30
End: 4:00
Most users would expect this to equal 30 minutes, even if the underlying timestamps were actually:
3:30:00 → 4:00:54
If seconds were included, the calculation could show 31 minutes, which would not match the times displayed on the chart.
By rounding each timestamp down to the nearest minute before calculating the difference, Xchart ensures:
The duration always matches the displayed times
The calculation remains consistent and predictable
Seconds and milliseconds do not cause confusing off-by-one minute results
Converting Minutes to Anesthesia Units
After Xchart calculates the total anesthesia minutes, it converts that time into anesthesia units.
The calculation is simple:
Divide the total minutes by 15
One anesthesia time unit equals 15 minutes.Round the result to one decimal place
Example:
Minutes | Calculation | Units |
30 minutes | 30 ÷ 15 | 2.0 units |
37 minutes | 37 ÷ 15 | 2.5 units |
52 minutes | 52 ÷ 15 | 3.5 units |
Summary
Anesthesia Minutes
The difference in whole minutes between Anesthesia Start and Anesthesia End, with both timestamps rounded down to the nearest minute.
Anesthesia Units
Total Minutes ÷ 15, rounded to one decimal place.
This approach ensures the calculated duration always matches the times shown on the anesthesia record while producing consistent billing units.