Maintain Time in Wpf

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C#

WPF

programming

I am creating a WPF application.I want to maintain time in my application meaning customers may rollback system time and used my application(Example.for some software If license is expired and system time is rollback but still software will work)

I want to maintain time.I found three ways
i)Timer in Database.
ii)Timer in in my application.
iii)Different service which update in database and I will get the real time.


If you guys have any suggestion which way should I go for OR you have any other suggestion different from above.
Please let me know