Code
T8001 date-by-javascript
In a plain definition, ==, !=, ===, !== or - stands between two moments, written or handed to calc, or a moment stands inside a text with values. It is a warning. JavaScript holds two moments to be two things, and writes one in the zone and the language of the server, so its meaning is not the one that is meant.
Details
The check reports it where it can see that both values are of the type date: a field of an input, a column of a row that db handed, now, and the answer of later and earlier. <, <=, > and >= between two moments mean what they say, and are not reported.
The fix
Use between(a, b, 'ms'), which is 0 for the same moment and the time from one to the other. Write a moment into a text with concat(...), which writes it in the standard form.