• Introduction
• Overview
• Why does Noda Time exist?
• Installation
• Core
• Core concepts
• Choosing (and converting) between types
• Core types quick reference
• Design philosophy and conventions
• Text
• Text handling
• Patterns for Duration values
• Patterns for Offset values
• Patterns for Instant values
• Patterns for LocalTime values
• Patterns for LocalDate values
• Patterns for LocalDateTime values
• Patterns for OffsetDateTime values
• Patterns for ZonedDateTime values
• Patterns for Period values
• Advanced
• Date and time arithmetic
• BCL conversions
• Serialization
• Calendars
• Threading
• Trivia
• Library
• Unit testing with Noda Time
• Updating the time zone database
• Mono support
• Limitations of Noda Time
• Current roadmap
• Version history

Patterns for Period values

Currently, the Period type doesn't support custom patterns, but two predefined patterns which are exposed in PeriodPattern:

Roundtrip (PeriodPattern.RoundtripPattern)

This pattern performs no normalization of the period - it simply writes out the value of each component of the period (as determined by its units). The format aims to be at least reminiscent of ISO-8601, and in many cases it will be compatible with ISO-8601, but it shouldn't be used in places where ISO compliance is required.

The format is:

P (date components) T (time components)

Where each non-zero component within the period is specified as its value followed by a unit specifier from this list:

• Y (years)
• M (months in the date portion)
• W (weeks)
• D (days)
• H (hours)
• M (minutes in the date portion)
• S (seconds)
• s (milliseconds)
• t (ticks)

The T is omitted if there are no time components.

This format differs from ISO-8601 in the following ways:

• Values are always integers; the ISO value of PT10.5S is invalid in this pattern, for example
• Values can be negative
• The s and t units aren't part of ISO

Normalized ISO-like (PeriodPattern.NormalizedIsoPattern)

This pattern normalizes the week, day and time parts of the period before formatting (even if the period only contains weeks, currently), assuming that a week is always 7 days and a day is always 24 hours. The result of the normalization removes weeks entirely, so a period of 2 weeks becomes 14 days. The month and year components are left alone, as they may vary in duration. The result of the normalization is then serialized in a way which is mostly compatible with ISO-8601.

The general format is as for the roundtrip pattern, but without the s and t units; weeks are currently never formatted due to normalization.

Only non-zero components are formatted. The exception to this is the zero period, which is formatted as "P0D".

Any fractional seconds are formatted using a period as a decimal separator, with a leading 0 if necessary. So for example, a 500 millisecond period is formatted as PT0.5S.

While this pattern is more ISO-like than the roundtrip pattern, it can still produce a text representation which is not valid in ISO, as it values may be negative. Any valid ISO representation can be parsed correctly, however.

Methods on Period

At the time of this writing, there are no methods performing parsing within Period, and only the parameterless ToString method is supported, which always uses the roundtrip pattern described above. If patterns based on text representations are ever supported, these methods will be implemented on Period in the normal way.