Yes, you can change the date. There is a field on the Add $ screen called Transaction Date. It gets pre-filled with today's date, but you can tap on the field and a date picker will pop up, so you can enter whatever date you want.
If you are using the Compact View, there won't be a label on the field saying "Transaction Date" but it is still there, with today's date in it. Tap it to change it.