Elapsed time in several useful units
Toolmera breaks the interval into whole days, remaining hours, minutes and seconds, then also shows the total duration in hours, minutes and seconds.
This is useful for shifts, sessions, production windows, travel segments and other elapsed-time calculations.
Local date-time inputs do not name a time zone
The browser interprets datetime-local inputs in the local environment. That is appropriate for same-zone elapsed time but it is not a substitute for named-zone conversion.
For events in different locations or daylight-saving-sensitive scheduling, convert the instants with Time Zone Converter first.