If you have multiple books and don't want to enter the value manually for each, another solution would be like this:
- In your SQL Viewer/Editor export the data you want to csv. If your SQL Editor does not support exporting to csv, look for another one in google.
- Use the Import List plugin to import the timestamps. Import List does not support importing to the original timestamps field, so you will have to import into a custom date column.
- Use Action Chains SFE template to copy the timestamps from you custom column.
Notes:- For your custom date column, use the iso format. It guarantees parse_date is not confused between months and days, it also includes times and time zone.
- Import List can match books using uuid. So make sure to choose that for matching books.
- If you use this method for copying values FROM custom columns, you will find the resulting csv file without the uuid field. In which case you will have to also export the books table to another csv file, and link them using VLOOKUP in excel.
- You only need to do steps 2 and 3 if you are importing into timestamps. Since Import List supports all other columns, you can directly import into them, with caveat mentioned above for custom columns.
Edit: An earlier version of this post was deleted, because I realized after posting that I needed to check some things in calibre, which I did not available at the time. Sorry to the mods for the inconvenience.
Edit2: Instead of using sql viewer to export to csv, it is better to open the backup library with calibre itself and use the catalog function to export to csv.