change updated date when translation is marked proofread
We are using APIs to sync translations from Poeditor into our system, we find it useful to overwrite only the terms in our database which have been marked with proofread on poeditor, so the plan is to setup a daily job to get all proofread translations from poeditor which have been updated less than 1 day ago, and overwrite them in our system. But this won't work since we noticed that toggling "proofread" doesn't change the update date on translations
The update date refers to the date when the translation was last edited, so it indeed cannot be used in the case you described.
What you could do is keep all the proofread terms in a JSON for each language and compare them with the next export, to see what was already proofread and what is new, and then send to your database only the newly proofread strings.
Note that you can also export all proofread translations only when the language is 100% completed, with callbacks: https://poeditor.com/kb/how-to-use-poeditor-callbacks