Sleep Time and Timezone changes

I am a pilot, have to travel for work everyday. 

Yesterday I was at home base and then took a flight to London. 

Departed home base at 0900 local to land in London at 1400 local.

At home base my also showed 7 hrs.

After landing in London and waking up the next day my sleep time is way off. Shows 30+ hrs of sleep

I used Fenix 7x till a day before and epix has been on my wrist only for 2 days. I'm guessing the software is the same.

I've never had so much error on Fenix 7x.

Can someone please explain this error at garmin. Or anyone who has had this as well?