fix #13797

[timotheecour]

• fix DateTime initializes to invalid state by default #13797
• failure unrelated (see nim CI fails with this package ba0f3/telebot.nim#49)

[Clyybber]

This is not a fix for #13797.
This merely "fixes" the repro snippet.
From the issue:

Without manual initialization, the common programming pattern of comparing a value to a default value is not possible

[timotheecour]

Without manual initialization, the common programming pattern of comparing a value to a default value is not possible

from my comment in that same bug report #13797 (comment)
this works:

when true:
  import times
  var d:DateTime
  if d == DateTime.default:
    echo "unchanged"

(which is why i wanted to add isDefault to stdlib (maybe in sugar) which would just be: if d.isDefault , see #13526)

[Clyybber]

The issue here is that the default is bogus.

[timotheecour]

The issue here is that the default is bogus.

in what sense? because the month is 0, which is invalid?
one way to fix that would be ot make months 0-based using an implicit offset of 1 (transparent change for users). But I'm not convinced yet thats needed; having an invalid default value is actually useful to check whether a value was initialized or not