QDateTime

QDateTime is a class in the Qt Core module that encapsulates date and time information. It combines a calendar date and a time of day with a time specification that clarifies how the value should be interpreted. A QDateTime object generally comprises a QDate, a QTime, and a time specification such as local time, UTC, or an offset from UTC.

A QDateTime can be valid or invalid. Use isValid() to check before use. It provides accessors and mutators for the date and time, including date(), time(), setDate(), and setTime(). The object can be converted to and from the underlying QDate and QTime components, and it can be compared with other QDateTime instances.

Construction and conversion options include a default constructor, and constructors such as QDateTime(const QDate &, const QTime &, TimeSpec = LocalTime). Static helpers create instances from common sources, for example currentDateTime() and currentDateTimeUtc(). There are also factories like fromSecsSinceEpoch(long seconds, int offsetFromUtc = 0) and fromMSecsSinceEpoch(qint64 milliseconds). Formatting and parsing are supported via toString() with a specified format and fromString() to parse textual representations.

Time specification is represented by the TimeSpec enum, which includes LocalTime, UTC, and OffsetFromUTC. Some Qt versions also support interacting with explicit time zones through the QTimeZone class. Methods such as setTimeSpec() and setTimeZone() allow changing how the stored moment is interpreted.

QDateTime interoperates with QDate and QTime and supports arithmetic operations such as addDays(int), addSecs(int), and addMSecs(int). It also provides conversions to Unix epoch times through toSecsSinceEpoch() and toMSecsSinceEpoch(), facilitating serialization and timestamp handling.