Every time you get or spend Gold, Ledger automatically adds a new record, saying who (which character), when (date and time, localized to your time zone), how much and why (loot, theft, quest reward, guild store, etc...).
Type '/ledger' (or set a key binding in the control settings) to open Ledger's window. There you can see a history of all your Gold transactions, filter by period, character and also a summary of your finances.