To reproduce:
1.Open users attached project "Negative Delta Time Test.zip"
2.Drag "test.cs" script from project window to Main Camera in the hierarchy
3.Enter play mode
4.Observe in the left top corner delta time
5.Pause the play mode
6.Open Date and Time Preferences and change the date to day before
7.Un-pause the play mode
8.Observe as the delta time became 1E-05
9.If not, pause the play mode again and change the date to day before that

Expected result: delta time always reports correct value
Actual result: by changing the date delta time becomes 1E-05

Reproduced on:5.4.1f1 5.5.4p1 5.6.1f1 2017.3.0a2

Notes: also reproducible on build. Happens ONLY on MAC. Tested: macOS Sierra 10.12.5, macOS High Sierra 10.13 Beta (17A306f) .
Changing time back to the present date fixes the issue.