Excel uses numbers to represent dates and times. Jan. 1, 1900 is day 1, Jan.
2,
1900 is day 2. Jan. 1, 1950 is day 18,264. Jan. 1, 2008 is day 39,448. Jan.
1, 2009
is day 39,814. A fast way to see the date serial number for a date is to
enter
the date in a cell then press Ctrl+Accent grave (`) - the key above tab and
left
of the 1 key Press Ctrl+Accent grave again to return to normal. Excel uses
the
numbers 1 (Jan. 1, 1900) through 2,958,465 (Dec. 31, 9999) to represent
dates. Is a number a number or a date? It depends on how you interpret it.
You can use those numbers for calculations or format them as dates. If you
have
entered a date and time, Excel stores the date as the integral part of the
number
with the time as a decimal fraction. For example if I enter: Jan 1, 2008
12:00 PM
Excel stores that as 39448.5 where the day is 39,448 and the time is .5
representing:
24 hours * .5 = 12 - noon. Excel's times start with 0.0 representing 12:00
AM
- i.e. midnight. So if you enter Jan 1, 2008 9:31 AM Excel stores that as:
39448.396527778. 24 hours * .396527778 = 9.516666667 hours, which is 9:31 AM
If you enter 3:00 AM, no date, Excel stores that as 0.125 (3/24). The 0
represents
the fictitious date of Jan. 0, 1900. If you enter 3:00 PM, Excel stores that
as
0.625 (15/24). Dates and times are just numbers. Formatting those numbers as
dates
and times is for visual display. Many people confuse the formatted value in
a
cell with the value in the cell. When you format a cell, Excel does not
change the
value in the cell; Excel simply displays the value in the cell in the way
you want
to see it.
Tyro
