Steps to reproduce

with Elixir v1.13

iex(1)> now = ~U[2023-01-01 10:20:30Z]
~U[2023-01-01 10:20:30Z]
iex(2)> Timex.shift(now, hours: 1)
~U[2023-01-01 11:20:30Z] # OK

with Elixir v1.14

iex(1)> now = ~U[2023-01-01 10:20:30Z]
~U[2023-01-01 10:20:30Z]
iex(2)> Timex.shift(now, hours: 1)
~U[2023-01-01 11:20:30.000000Z] # precision changes unnecessarily

Description of issue

• Elixir v1.14 changes DateTime.add/4 behaviour to preserve the maximum precision of given parameters.
  • commit: elixir-lang/elixir@5a583c7
  • relates to: Time.add behaviour changed in 1.14 elixir-lang/elixir#12303
• Timex.shift/2 uses DateTime.add/4 with :microsecond precision to apply time-shift result.

  • timex/lib/datetime/datetime.ex

    Line 450 in e1c4d42

    DateTime.add(datetime, shift, :microsecond, Timex.Timezone.Database)

This causes unnecessary precision conversions in Elixir v1.14 and later.