Soenneker.Extensions.DateTimeOffsets.Months

Month-boundary extensions for DateTimeOffset, including time-zone-aware boundaries returned as UTC instants.

Installation

dotnet add package Soenneker.Extensions.DateTimeOffsets.Months

Offset-preserving boundaries

Use these methods when the value's existing calendar month and offset are already the frame of reference. They do not apply time-zone rules.

using Soenneker.Extensions.DateTimeOffsets.Months;

var value = new DateTimeOffset(2024, 3, 15, 14, 30, 0, TimeSpan.FromHours(-5));

DateTimeOffset start = value.ToStartOfMonth();
// 2024-03-01 00:00:00 -05:00

DateTimeOffset end = value.ToEndOfMonth();
// 2024-03-31 23:59:59.9999999 -05:00

Available operations are ToStartOfMonth(), ToEndOfMonth(), ToStartOfPreviousMonth(), ToEndOfPreviousMonth(), ToStartOfNextMonth(), and ToEndOfNextMonth().

Time-zone month boundaries

Use the Tz methods when the input represents an instant and the month must be determined in a particular time zone. The result always has a zero offset.

TimeZoneInfo eastern = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
var instant = new DateTimeOffset(2024, 3, 15, 19, 30, 0, TimeSpan.Zero);

DateTimeOffset startUtc = instant.ToStartOfTzMonth(eastern);
// 2024-03-01 05:00:00 +00:00

DateTimeOffset endUtc = instant.ToEndOfTzMonth(eastern);
// One tick before 2024-04-01 04:00:00 +00:00

The time-zone methods are ToStartOfTzMonth(), ToEndOfTzMonth(), ToStartOfPreviousTzMonth(), ToEndOfPreviousTzMonth(), ToStartOfNextTzMonth(), and ToEndOfNextTzMonth().

End methods are inclusive: they return one tick before the following month begins. Boundaries follow the supplied time zone's transition rules; if a historical transition skipped local midnight, the start resolves to the first valid local time in that month.