When would you use DateTime, DateTimeOffset, and TimeZoneInfo, and how would you model time across an API and database?

DateTime, DateTimeOffset, and time-zone boundaries in .NET

Distinguishes instants, local calendar values, offsets, and named time zones so APIs and persistence survive daylight-saving and locale boundaries.

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For an event that happened at a precise instant, I prefer DateTimeOffset at boundaries because the value includes an offset and maps unambiguously to UTC. A UTC DateTime can also represent an instant when its Kind is handled consistently, but an unspecified or local value is easy to misinterpret. TimeZoneInfo applies named time-zone rules when converting for users. A date-only business value such as a birthday uses DateOnly, while a local opening time may use TimeOnly plus the location's zone and business rules.

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DateTime, DateTimeOffset, UTC, offsets, TimeZoneInfo, daylight-saving transitions, local calendar values, serialization, persistence, and testing.

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Time bugs usually come from mixing an instant on the global timeline with a local business date or future wall-clock schedule. The type and stored data must preserve the meaning the product actually needs.
For an event that happened at a precise instant, I prefer DateTimeOffset at boundaries because the value includes an offset and maps unambiguously to UTC. A UTC DateTime can also represent an instant when its Kind is handled consistently, but an unspecified or local value is easy to misinterpret. TimeZoneInfo applies named time-zone rules when converting for users. A date-only business value such as a birthday uses DateOnly, while a local opening time may use TimeOnly plus the location's zone and business rules.

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Treating a numeric offset as a permanent time-zone identity.
Storing server-local DateTime values with unspecified meaning.
Using one timestamp type for birthdays, durations, and instants.
Adding fixed hours to implement calendar scheduling.

When would you use DateTime, DateTimeOffset, and TimeZoneInfo, and how would you model time across an API and database?

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