Fix time range in test cases

[spencerjanssen]

SQL Server doesn't support leap seconds. Resolves #56.

FYI @chrisdone

[chrisdone]

Can you explain what’s happening with these numbers?

[spencerjanssen]

We want to avoid TimeOfDay values which are greater than or equal to 23:59:60 because SQL Server doesn't allow them.

The old upper limit of 86400 seconds represents 23:59:60, our new upper limit represents 23:59:59. The Arbitrary instances add some fractional seconds to this value which is fine because the end result is still less than 23:59:60.

Similarly 1440 minutes is 23:60 which we've adjusted to 1439 or 23:59.

Clearly this is tricky and warrants some explanation in the code!