Questions tagged [datetime]

A DateTime object in many programming languages describes a date and a time of day. It can express either an instant in time or a position on a calendar, depending on the context in which it is used and the specific implementation.

• In lua, os.date and os.time are provided as part of lua's standard library for working with date and time.

• In sql the data types TIMESTAMP [WITHOUT TIME ZONE] and TIMESTAMP WITH TIME ZONE are collectively referred to as timestamps. (And the data types DATE, TIME, and TIMESTAMP are collectively referred to as datetime types.)

• In sql-server, datetime is a type that represents a date and time of day. It carries no time zone context, so it is a position on a calendar, not a moment in time.

• In mysql, DATETIME values represent a date and time of day. They carry no time zone context, so they are positions on a calendar, not a moment in time. TIMESTAMP values represent a moment in time, and are based on UNIX time. When MySQL stores TIMESTAMPs, it converts them from the current connection's time zone setting to UTC. When displaying them it converts them back.

• In .net, DateTime is a structure that is typically expressed as a date and time of day. It represents either an instant in time, or a position on a calendar. The precise meaning is dependent on the value of its Kind property.

• In java, Instant is a class that represents an instant in time. Before Java 8 jodatime was a popular java library, DateTime is a class which represents an instant in time, with reference to a particular time zone.

• In python, datetime is an object which represents a date and time of day. The precise meaning is dependent on the value of its tzinfo property. It is also the name of the module that provides date, time, datetime, and related objects.

• In php the DateTime class is a representation of a instant in time, with reference to a particular time zone.

• In fortran, the time and date manipulation library datetime-fortran can be used.

• In javascript, a Date instance represents a single moment in time. Date objects are based on a time value that is the number of milliseconds since 1 January, 1970 UTC. That is, they are UNIX time values in milliseconds.

• In r, the classes "POSIXlt" and "POSIXct" represent calendar dates and times.Subtraction of two date-time objects is equivalent to using difftime. Class "POSIXct" represents the (signed) number of seconds since the beginning of 1970 (in the UTC time zone) as a numeric vector. Class "POSIXlt" is a named list of vectors representing sec, min, hour et al

• In excel, Microsoft Excel for Windows uses the 1900 date system, by default. Which means the first date is January 1, 1900. a Date and Time function can be used to manipulate the year/date and time/hour/minutes values. The date/time in Excel is stored as a number. Where the decimal part range from 0.0 to 0.99988426 represent 0:00:00 (12:00:00 AM) to 23:59:59 (11:59:59 P.M.), and the integer part range from 0 to 9999 represent days. But Excel's date representation is slightly off in the first two months of calendar year 1900.

Helpful articles

• SQL Server DateTime data type considerations and limitations