Keeping Steam aware of played time?

I work similarly (merchant navy seaman) and have same issue.

I've perused a few local topics about offline mode, such as this one from 5 years ago, but it would appear that while steam may internally log your hours for potential refunds (to avoid potential scams I suppose, so you can't finish a 50 hour game offline and then refund with 0.2 hours official playtime or what), playtime doesn't get updated whatsoever when playing offline. Though I have also seen some people post to the contrary saying that it depends on the game and some games sync total hours whenever you next sync with steam.

The question would be, what do you need the hours for (achievements, bragging rights, or to show a GA host that you're actually playing)? Maybe going from there, someone would be able to help you, if it is at all possible.

It sounds like a potential goldmine for returning games you've actually played. I imagine, though, that you don't want to screw the game developers.

Have you considered getting an international SIM card and data plan for your cell phone, and hotspotting? Or are you too remote even for cell reception?

my internet is kinda garbage. i would say like 30% of my play time or more is offline. why i card farm. some games i will have 50+ hours in and you dont have any card drops cause it was all offline. im not gonna leave my pc online with games open for 7 hours to get 3 cards after i have 100% them

Since you can still get the achievements in offline mode the only method I can suggest is write the amount of time you played offline on a note or something and when you're back home idle the game for the same amount of time while you do something else. You can even schedule your computer to shutdown at the exact time you want to finish idling if you don't have time to stop it manually.

You could use something like ASF to 'play' the game for you when you're connected to the internet again, but then you would need to know how long you played the game in offline modus, and I don't know if that data can be accessed anywhere...

After all, since the game you will play as offline, you will not spend internet, so you just need to turn on your phone's internet (if you can use it) and appear online on steam.

It sounds like you could benefit more with games from GOG or other DRM-free sources that don't require any connectivity at all post-installation.