A type that specifies a format for the time period in a date format style.
The type ``Date/FormatStyle/Symbol/DayPeriod`` includes static factory methods that create custom ``Date/FormatStyle/Symbol/DayPeriod`` objects.
|Factory variable|Description|
|---|---|
| ``conversational(_:)`` | Conversational abbreviated period. For example, `at night`, `nachm.`, `iltap`.  Conversational narrow period. For example, `at night`, `nachmittags`, `iltapäivällä`.  Conversational wide period. For example, `at night`, `nachm.`, `ip.` |
| ``standard(_:)`` | Abbreviated period. For example, `am`.  Narrow period. For example, `a`.  Wide period. For example, `am`. |
| ``with12s(_:)`` | Abbreviated period including designations for noon and midnight. For example, `mid.`  Narrow period including designations for noon and midnight. For example, `md`.  Wide period including designations for noon and midnight. For example, `midnight`. |
The day period format style may be uppercase or lowercase depending on the locale and other options.
For more information about formatting dates, see the ``Date/FormatStyle``.