Assets History records down all of your various coins' deposit and withdrawal history as well as an account 'statement' of all your trading activities performed in the previous 24 hour time period. This statement summarises all your account's trading fees, funding fees and Closed P&L at UTC 0000 based on the trading activities conducted on the previous 24 hour time period.
For example, using the screenshot below
The figure 0.00167165 BTC recorded on 2019-09-14 00:00:03 UTC consisted of all the account's trading fees, funding fees and Closed P&L trades that were performed from 2019-09-13 00:00:00 UTC to 2019-09-13 23:59:59 UTC.
Note: The timing shown inside your Assets History will follow your computer operating system's time settings. If you are in Beijing, China, your Assets History will display all timings in your timezone GMT+8.