I have the same problem, and in addition, the activity execution time is delayed by 11 hours on Strava.

It's reassuring that it's not my fault.

I have exactly tha same issue, Have you got any solution?

I replaced the watch with a Zeblaze stratos 2 ultra, which uses the Gloryfit app. It's perfect.

Hello ​@tcshooker , ​@KamilB , ​@GScheeren !

Sorry for the differences you're seeing in your activities. These data discrepancies could either be a result of the way your file is formatted or the way Dafit is choosing to analyze the data.
 
To provide context, Garmin set the industry standard with FIT and TCX file formatting (read more here and here). We use Garmin's file formats in order to upload and analyze the data in your file. If Dafit isn't following these standards or if the company has made file formatting modifications to accommodate device or app specific features, then we may not be able to correctly parse the files. This could lead to differences in your activity stats when compared between platforms.
 
Another consideration is whether Dafit is using a different method than Strava when calculating your stats. For example, consider the process of determining how much resting vs moving time is in an activity. What constitutes a rest? Is it when you're at rest for 1, 3, 10, or 20 seconds? And what does your speed have to fall below in order for you to be considered at rest? 1 second might capture too many false positives and 20 seconds may be too strict. One calculation isn't necessarily correct or incorrect, but we do feel we're using standards that most athletes would agree upon.
 
We understand our athletes use hundreds of different devices and apps and are doing our best to accurately analyze each file regardless of the differences in file formatting. We're always working to improve our athletes' experience and we will pass this feedback along to our engineering teams.
 
I hope this helps. If you have any other questions, please let me know!
 

Thanks for the answer. It doesn't matter to me anymore because I sold the watch that used the Dafit app. The current one works fine with the Gloryfit app. The doubling of time is definitely not because of the rest periods because there weren't any. It simply became twice as valuable.

How did you link the da fit app to strava, it’s not working for me. Did you do something special? 

Nothing special. Just like it said in the app.