Why my date on Z10 STL-1 always reset after doing Reboot ?

date on my Z10 STL-1 with OS 10.3.01.1154 always reset to 14 Nov 2014 (actually it's happened since my OS 10.2 but i dont know when exactly) , i've search on internet and found many same problems like me.
but there are no solution.

if the handheld connected on charger, then the date will not reset (just like another people)..

thanks for your attention (and sorry for my very bad english)

have you tried OS 10.3.1 and does this still happen?

Your date and time is usually pulled from the sim card. Do you have a sim inserted?

PassportSQW100-1/10.3.0.1418 O2 UK

I have same problem on 10.3.1 and yes i have a sim inserted.

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Any solution to this problem?

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