epoch is INHERENTLY timestamped it's seconds since January 1, 1970 (midnight UTC/GMT). it'd be useless if it was just "you know midnight _somewhere_ on Jan 1 1970... pfft it was a long time ago. who cares"
When you go one hour back for daylight savings, you can't tell with just epoch if it's the first or second time you're at that time. With timezones you can, since it switches between PST and PDT.
I don't know that much about epoch, but isn't the point of it to be completely independent of stuff like timezones or daylight savings? Doesn't it track every second since 1970 no matter if meanwhile time jumped back or forward in some countries?