time .is_valid() is not just a check for 1970-01-01

[sjpilot]

Feedback

time is_valid() check is not just 1970-01-01, it is 2019-01-01 or onwards per https://api-docs.esphome.io/time_8h_source#l00073

URL

https://esphome.io/components/time/

Additional information

I will provide a pull request shortly per current...sjpilot:esphome-docs:patch-1