Reduced to the essential, Nordcodes Time Calculator lets you add (+) and subtract (−) times or durations.
Times and durations can be negative, so there is also a sign change.
But multiplication (×) and division (÷) are not available, due to the fact, that e.g. 1h30m × 2h45m cannot produce a meaningful result and changing between times / durations (1h30m) and Numbers (4) on the display seems confusing to me, in my opinion leading to an inferior product.
Also not available are ads and the collecting of data, that often is associated with ads. Time Calculator is guaranteed to be privacy-friendly and free of advertisements, no data is sent "home" or somewhere else.
This is why it is not completely free moneywise, its a little consideration for my work. Thank you so much, for helping to develop ad-free and privacy-friendly software, by buying this app.