Class Microsoft.VisualBasic.DateAndTime Syntax Dim result As Long = DateDiff(interval, date1, date2[, _ dayOfWeek[, weekOfYear]])
interval (required; String or DateInterval enumeration) A string expression or Microsoft.VisualBasic.DateInterval enumeration item indicating which part of the date to report in the return value. The following table lists both the string and enumeration choices. String | DateInterval | Description |
|---|
d | Day | The difference in days | y | DayOfYear | The difference in days | h | Hour | The difference in hours | n | Minute | The difference in minutes | m | Month | The difference in months | q | Quarter | The difference in quarters | s | Second | The difference in seconds | w | Weekday | The difference in weeks, based on counting individual days | ww | WeekOfYear | The difference in weeks, based on full calendar weeks | yyyy | Year | The difference in years |
date1 (required; Date) The first date from which to calculate the difference.
date2 (required; Date) The second date from which to calculate the difference. To return a positive result, this date should occur after date1.
dayOfWeek (optional; FirstDayOfWeek enumeration) Indicates the first day of the week. One of the following Microsoft.VisualBasic.FirstDayOfWeek enumeration members: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or System (to use the regional default). If omitted, Sunday is used.
weekOfYear (optional; FirstWeekOfYear enumeration) Indicates which week counts as the first week of a given year. One of the following Microsoft.VisualBasic.FirstWeekOfYear enumeration members. Value | Description |
|---|
System | Uses the system-defined value | Jan1 | Uses the week in which January 1 appears | FirstFourDays | Uses the first week of the year that has at least four days in it | FirstFullWeek | Uses the first week of the year that has a full seven days in it |
If omitted, Jan1 is used.
Description The DateDiff function calculates the number of time intervals between two dates. For example, you can use the function to determine how many days there are between January 1, 1980, and May 31, 1998. Usage at a Glance To calculate the number of days between date1 and date2, you can use the DateInterval constants Day or DayOfYear or the string literals "d" or "y." When interval is Weekday or "w," DateDiff returns the number of weeks between the two dates based on the number of days between the two dates. When interval is Week or "ww," DateDiff returns the number of weeks by first considering the full weeks in which date1 and date2 appear and then counting based on the first day of each of these weeks. The dayOfWeek parameter is significant in this calculation. In the calculation, the interval is determined by subtracting date1 from date2. If date1 appears before date2 in chronological order, the return value will be positive; if date1 appears after date2 in chronological order, the return value will be negative. The expression DateDiff("yyyy", #12/31/2005#, #1/2/2006#) returns 1, even though only two days have elapsed. Similar results occur for related differences in other intervals. DateDiff considers the four quarters of the year to be January 1 to March 31, April 1 to June 30, July 1 to September 30, and October 1 to December 31.
Version Differences VB 6 lacks the DateInterval enumeration and therefore only accepts a string for the interval argument. VB 6 supports a number of constants beginning with vb... (such as vbSunday) as values for the dayOfWeek and weekOfYear arguments. While these are still supported in .NET, the new FirstDayOfWeek and FirstWeekOfYear enumerations are preferred.
See Also DateAdd Function |
