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30/360

Calculates the number of days between two dates using the 30/360 day count basis (12 months x 30 days).

Input form: (from date) 30/360 (to date)

where dates are specified with reference to the zero day value. In practice, you can use the [DATE] key to input date values.

Example: Find the number of days between May 16th, 2001 and January 9th, 2005 using the 30/360 basis. Assume that you enter dates in M-D-Y format.

5 [DATE] 16 [DATE] 2001
[30/360]
1 [DATE] 9 [DATE] 2005
[ENTER]
Displays: 1313

30E/360

Calculates the number of days between two dates using the 30E/360 day count basis. This function is identical to 30/360, except that European rules are used for the month of February.

DATE

Use the [DATE] key to enter a date and optional time. The input is converted automatically to a day calendar value. For most users, the date format will automatically be set to their preferred notation. Otherwise it will default to Month-Day-Year (M-D-Y).

Example: Key in May 16th, 2001. Assume that you enter dates in M-D-Y format.

5 [DATE] 16 [DATE] 2001
[ENTER]
Displays: 730621 (Rata Die)

Also use the [DATE] key to convert a numerical value to a date representation.

For example:

730621
[DATE]
Displays: 05/16/2001

For more information, see the introductory section on Date Calculations.

DLHRS

The function is available from the [MISC] menu key, and calculates the number of hours of daylight, given a day of year number and latitude.

Input form: (doy) DLHRS (latitude)

Latitude should be expressed in units of the calculator's angle mode.

Range & Accuracy

Day Range: 1 (Jan 1st) to 366
Latitude Range: -65 to +65 (degrees)
Accuracy within 40º of Equator: +/- 1 minute
Accuracy within 60º of Equator: +/- 7 minutes (typically +/2 minutes)

Example: How many hours of daylight in New York today? (New York's latitude is 40.78 degrees).

[DOY] [TODAY]
[ENTER]
Displays: 53 (get today's day number*)
[DLHRS] 40.78
[ENTER]
Displays: 10.92*...

* Actual value depends on the current date.

Reference: "A Model Comparison for Daylength as a Function of Latitude and Day of the Year", Ecological Modeling, Volume 80 (1995) pp. 87-95.

DOW

Calculates the corresponding day of week, given a date input, where Monday always has a value of 1.

Example: What day will it be on March 17th, 2029?

[DOW]
3 [DATE] 17 [DATE] 2029 (March 17, 2029)
[ENTER]
Displays: 6

The value of 6 represents Saturday. The number value for Sunday may be either 0 or 7, depending up your setting for the first day of the week in the Options Window.

DOY

Calculates the corresponding day of the year, given a date input, where 1 is the first day of the applicable year.

TODAY

Returns the current date and time from the PC clock. It may return either your local time or Universal Time, as configured in the Options Window.

Example: What date will it be in 321 days from now?

[TODAY] (today's date & time from PC clock)
[+]
321
[ENTER]
Displays: 732306.3899... (depends on current time)

and...

[DATE] Displays: 12/26/2005 +09:21:32.

For more information, see the introductory section on Date Calculations.

WKNO

Given a date input, WKNO returns the corresponding week of the year according to the ISO8601 Standard, which defines the first week of the year as being the one which contains the 4th of January. The result may be between 1 and 52, or 53 for leap years and is affected by the "Week Start" setting in the Options Window.