One Galleon is 17 Sickles and one Sickle is 29 Knuts... The wizarding currency isn’t too simple or practical, is it? Muggles also have struggled for ages with overcomplicated, inconsistent systems of units. But then we adapted the SI – and since then we got used to using this simple, decimal system.
There is one thing though that we still measure in strange units. 60 seconds go in a minute, 60 minutes go in an hour, 24 hours go in a day. There’s 365 days in a year, except when it’s 366, and they can be divided into 52 weeks of 7 days, with some days left over, or alternatively into 12 months of 28, 29, 30 or 31 days each, depending on... reasons.