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Date Time string formatting in ASP.NET

Nauman — Thu, 24 Dec 2009 11:15:15 +0000

With the following code you can format a DateTime within a Databind.

<%# DateTime.Parse(Eval("DateModified").ToString()).ToString("MM-dd-yyyy")%>

Some more format specifiers that can change format of datetime objects the way it is required.

Format specifier	Name
d	Short date pattern
D	Long date pattern
t	Short time pattern
T	Long time pattern
f	Full date/time pattern ( short time )
F	Full date/time pattern ( long time )
g	General date/time pattern ( short time )
G	General date/time pattern ( long time )
M or m	Month day pattern
R or r	RFC1123 pattern
s	Sortable date/time pattern; conforms to ISO 8601
u	Universal sortable date/time pattern
U	Universal sortable date/time pattern
Y or y	Year month pattern

Calculating difference of dates in Oracle

Nauman — Wed, 18 Nov 2009 16:28:37 +0000

How to calculate difference between two dates in oracle, as subtraction of dates returns numeric value as difference. With some slight changes/enhancements we can track back the subtraction values to some readable date formats:

Here are some examples, these can also be amended for user convenience:

SQL> SELECT floor(((date1-date2)*24*60*60)/3600)
  2         || ' HOURS ' ||
  3         floor((((date1-date2)*24*60*60) -
  4         floor(((date1-date2)*24*60*60)/3600)*3600)/60)
  5         || ' MINUTES ' ||
  6         round((((date1-date2)*24*60*60) -
  7         floor(((date1-date2)*24*60*60)/3600)*3600 -
  8         (floor((((date1-date2)*24*60*60) -
  9         floor(((date1-date2)*24*60*60)/3600)*3600)/60)*60) ))
 10         || ' SECS ' time_difference
 11    FROM dates;

TIME_DIFFERENCE
--------------------------------------------------------------------------------
24 HOURS 0 MINUTES 0 SECS
1 HOURS 0 MINUTES 0 SECS
0 HOURS 1 MINUTES 0 SECS

SQL> SELECT to_number( to_char(to_date('1','J') +
  2         (date1 - date2), 'J') - 1)  days,
  3         to_char(to_date('00:00:00','HH24:MI:SS') +
  4         (date1 - date2), 'HH24:MI:SS') time
  5   FROM dates;

      DAYS TIME
---------- --------
         1 00:00:00
         0 01:00:00
         0 00:01:00

SQL> select numtodsinterval(date1-date2,'day') time_difference from dates;

TIME_DIFFERENCE
----------------------------------------------------------------
+000000001 00:00:00.000000000
+000000000 01:00:00.000000000
+000000000 00:01:00.000000000

SQL> SELECT floor((date1-date2)*24)
  2         || ' HOURS ' ||
  3         mod(floor((date1-date2)*24*60),60)
  5         || ' MINUTES ' ||
  6         mod(floor((date1-date2)*24*60*60),60)
 10         || ' SECS ' time_difference
 11    FROM dates;

TIME_DIFFERENCE
--------------------------------------------------------------------------------
24 HOURS 0 MINUTES 0 SECS
1 HOURS 0 MINUTES 0 SECS
0 HOURS 1 MINUTES 0 SECS

Find week start/end given week number

Nauman — Tue, 03 Nov 2009 14:32:43 +0000

I have a table with some dated records. I wanted to do some weekly reports on this data. MySQL has a nifty function dubbed WEEK() which will return a week number. It allows you to break your data into week long intervals very easily. For example, the following query will tell me how many records came in each week:

SELECT COUNT(*), WEEK(mydate)

FROM mytable

GROUP BY WEEK(mydate);

The problem here is, that the output is totally meaningless to me as I do not have a clue what does week 36 mean. What I really want is to have on the screen is a nice, human readable date interval – the beginning and ending date of any given week.

Surprisingly, this turns out the be a major pain in the ass. There is no simple function that will yield a week interval (or start/end date of a week) given a week number. You have to find these dates manually. Here is how I did it:

SELECT COUNT(*) AS reports_in_week, DATE_ADD(mydate, INTERVAL( 1-DAYOFWEEK(mydate) ) DAY), DATE_ADD(mydate, INTERVAL( 7-DAYOFWEEK(mydate) ) DAY)

FROM mytable

GROUP BY WEEK(mydate)

How does it work? The DAYOFWEEK() function returns an integer ranging from 1 (Sunday) to 7 (Saturday). So if mydate happens to be Tuesday we get the following statements:

DATE_ADD(mydate, INTERVAL -2 DAY)

which essentially means "subtract 2 days from mydate (which is that week’s Sunday) and also:

DATE_ADD(mydate, INTERVAL 4 DAY)

which yields the date of that week’s Friday.

How To Calculate the Number of Week Days Between two Dates

Nauman — Sun, 01 Nov 2009 16:16:21 +0000

If the start date and end date are both week days, then the total number of week days in between is simply:

(total difference in days) – (total difference in weeks) * 2

DateDiff(dd, @start, @end) – DateDiff(ww, @start, @end)*2

… since the DateDiff() function with weeks returns the number of week "boundaries" that are crossed; i.e., the number of weekends.
If you have a table of holidays, then you can simply subtract them out as well:

DateDiff(dd, @start, @end) –
DateDiff(ww, @start, @end)*2 –
(select count(*) from holidays where holiday_date between @start and @end)

Now, what if the start day or the end day is on a weekend? In that case, you need to define what to do in those situations in your requirements.
For example, if the start date is Sunday, Nov 20th, and the end day is Monday, Nov 21st — how many week days are between those dates? There’s no universal correct answer; it could be 0, or 1, or perhaps even "undefined" (null) depending on your needs.