I change s to hhmmss unit of time and get an error
In Mathcad 15 all OK
Prime like so:
But a:=...=... hhmmss does not work
As far as I remember this is not the first Prime bug which has to do with inline evaluation.
Maybe its not the inline evaluation this time but the way in which the "unit" hhmmss, which is a function in postfix notation, is automatically interpreted one time as the function and the other time as its own inverse function. Similar to °C, but with °C all is OK: