Date and Months of the Novel
#Months:
Their pretty similar to the months we have on Earth and just like on Earth there are 12 of them but since it's a fantasy world I feel it would break immersion if I just called them the regular month names so here they are:-
1.Januar
2.Februal
3.Marchal
4. Mayer
5.Apilut
6 .Junal
7 .Julias
8.Augustal
9.Septembiere
10.Octobal
11.Novemboral
12.Decembierre
I tried to make them sound familiar to out Earth month names so you can know what month I'm refering to without breaking immersion.
#Date System
The date system is day/month/year because that's the only correct method.
#Years
William was born in the year 5668,as of right now the year is 5678(ch-35).
The years before Zephyr was born and killed the demon king are now referred to as Before Zephyr Years or BZY for short these years are mentioned with (-) sign for example the year -129.
after killing Demon king he ruled for 400 years and since he killed the demon king at the age of 20 he ascended to Godhood at the age of 420,these years after his ascension are known as After Zephyr Years thus denoted as (+) but since you didn't skip maths class you know we don't need to show (+) signs with positive numbers, and since the story starts in the year 5668 and these years started 400 years after demon kings death.
The demon King has been dead for 6000 years
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Authors note:
Zephyr is basically Jesus
Gifts
-- Gift
received Weekly Power Status
-- Power
Ranking 
-- Power
stone