import re

am = ['a.m.', 'am', 'ante meridiem']
timeinp = 'reminder for 3:30 am'

a = "|".join(map(re.escape, am))
gettime = re.search(fr'\b(\d{{1,2}}):(\d{{2}})\s*(?:{a})', timeinp)
if gettime:
    print(list(map(int, gettime.groups())))
else:
	print("no match")