Replaced calendar.timegm by lookup tables

[codecov[bot]]

Codecov Report

Base: 95.94% // Head: 95.65% // Decreases project coverage by -0.29% :warning:

Coverage data is based on head (493d211) compared to base (f198c48). Patch coverage: 97.61% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #238 +/- ## ========================================== - Coverage 95.94% 95.65% -0.30% ========================================== Files 24 24 Lines 2195 2230 +35 ========================================== + Hits 2106 2133 +27 - Misses 89 97 +8 ``` | [Impacted Files](https://codecov.io/gh/log2timeline/dfdatetime/pull/238?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=log2timeline) | Coverage Δ | | |---|---|---| | [dfdatetime/interface.py](https://codecov.io/gh/log2timeline/dfdatetime/pull/238/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=log2timeline#diff-ZGZkYXRldGltZS9pbnRlcmZhY2UucHk=) | `96.61% <95.00%> (-1.89%)` | :arrow_down: | | [dfdatetime/definitions.py](https://codecov.io/gh/log2timeline/dfdatetime/pull/238/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=log2timeline#diff-ZGZkYXRldGltZS9kZWZpbml0aW9ucy5weQ==) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=log2timeline). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=log2timeline)

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