Years kept by hand
An example, with sample figures.
You've kept a sheet for years, and it no longer agrees with your bank.

You add each account, and on the web import each bank's CSV statement into it, choosing which column is which. Then you bring each balance to what your bank shows.
Paying off your card moves money between two of your accounts, so it stops counting as spending. Whenever you like, you export everything as CSV files.
Worth knowing
Import and export are on the web only. A sheet still wins on freedom of layout.
Import a statement