Programming .NET Windows Applications

Date and Time Values

Before you can fully understand date and time controls, you must first be familiar with how the .NET Framework deals with date and time values. Two different structures are provided for representing dates and times. The DateTime structure represents a specific point in time, while the TimeSpan structure represents a length of time. These structures are described in the next two sections.

DateTime Structure

Date and time values in the .NET Framework are typically represented with a DateTime structure. This structure is a value type representing a point in time, typically expressed with both a date and a time component. Like a class, it has constructors, fields, properties and methods, plus several operators, all for the purpose of allowing your code to represent and manipulate date and time values.

Time values in the .NET Framework are measured in units of ticks, each 100 nanoseconds long. Dates are measured as the number of ticks since midnight, January 1, 1 C.E. in the Gregorian calendar, unless a different calendar is explicitly specified.

Tip

The civil calendar in common use today is called the Gregorian calendar, named after Pope Gregory XIII. In 1582 he ordered changes to the calendar then in use to correct errors arising from the fact that a solar year is approximately 11 minutes short of 365 1/4 days. It is nominally based on the year of the birth of Jesus. Years prior to the birth of Jesus are referred to either as B.C. (Before Christ) or B.C.E. (Before ...