[This is preliminary documentation and is subject to change.]
Pattern which uses the normal ISO format for all the supported ISO
fields, but extends the time part with "s" for milliseconds and "t" for ticks.
No normalization is carried out, and a period may contain weeks as well as years, months and days.
Each element may also be negative, independently of other elements. This pattern round-trips its
values: a parse/format cycle will produce an identical period, including units.

C# | Visual Basic | Visual C++ |
public static readonly PeriodPattern RoundtripPattern
Public Shared ReadOnly RoundtripPattern As PeriodPattern
public: static initonly PeriodPattern^ RoundtripPattern
Assembly: NodaTime (Module: NodaTime.dll) Version: 1.2.0.0 (1.2.0)