.NET ticks converter

A .NET `DateTime.Ticks` value counts 100-nanosecond intervals since 1 January 0001. The number is large — about 638 quadrillion for a current date.

Counting from year one makes .NET ticks the odd one out and produces values around 6.4 × 10¹⁷, which exceeds JavaScript’s safe integer range — a tick value pasted into JavaScript as a Number loses precision in the last two digits. Use BigInt or strings. The other thing worth knowing is that `DateTime` carries a `Kind` — Utc, Local or Unspecified — which is *not* part of the tick value, so two identical tick counts can mean different instants depending on the Kind of the object they came from. That is a genuine design wart and the reason `DateTimeOffset` exists and is generally the better type.