If you're specifically asking about the amount of minutes/hours/days/weeks/... you can use:
Wie viele Minuten/Stunden/Tage/Wochen sind es noch bis zum Muttertag?
If you want to make it less formal, you can also leave out the "sind es", making it
Wie viele Minuten/Stunden/Tage/Wochen noch bis zum Muttertag?
If you want to make it even less formal (and potentially gramatically incorrect), you can even leave out "zum", making it
Wie viele Minuten/Stunden/Tage/Wochen noch bis Muttertag?
(I'd advise against using that, as it's somewhat common, but not very educated to say it like that)
If you do not care about the exact time or time format, you can also leave that out:
Wie lange noch bis zum Muttertag?
The answer will then usually be automatically adapted to the timeframe:
If you're waiting for a birthday close to midnight, the answer will be in seconds or minutes.
If you're asking about mothers day, the answer will most likely be in days or weeks.