Is it appropriate to use constants for dates?

Is it appropriate to use constants for dates?

pI use dates throughout an app. Rather than calculating the dates I need
each time I need them, I set them once in a constants file./p pI.e.
codedefine('NOW', date('Y-m-d'));/code/p pPreviously I used constants for
things like file paths, etc. Does it make sense to load a bunch of dates
like this, over, say, a single array of dates?/p