We have precise ways of writing times and dates.
"Saturday evening around 1-2am" is not one of the standards I'm familiar with, but it must be a standard because this was in a notification from a technology organisation, and they would know about such things.
Is that the "Sunday morning" part of Saturday evening?
If the Penny Black opens at 5am, and the sun isn't up yet and I left home on Saturday evening, what time is it, where am I, and more importantly, where are my trousers?