How to Subtract/Add Days From/To a Date

How to subtract/add days from/to a date?

Just subtract a number:

> as.Date("2009-10-01")
[1] "2009-10-01"
> as.Date("2009-10-01")-5
[1] "2009-09-26"

Since the Date class only has days, you can just do basic arithmetic on it.

If you want to use POSIXlt for some reason, then you can use it's slots:

> a <- as.POSIXlt("2009-10-04")
> names(unclass(as.POSIXlt("2009-10-04")))
[1] "sec"   "min"   "hour"  "mday"  "mon"   "year"  "wday"  "yday"  "isdst"
> a$mday <- a$mday - 6
> a
[1] "2009-09-28 EDT"

How to subtract days from a plain Date?

Try something like this:

 var d = new Date();
 d.setDate(d.getDate()-5);

Note that this modifies the date object and returns the time value of the updated date.

var d = new Date();
document.write('Today is: ' + d.toLocaleString());
d.setDate(d.getDate() - 5);
document.write('<br>5 days ago was: ' + d.toLocaleString());

Algorithm to add or subtract days from a date?

The easiest way is to actually write two functions, one which converts the day to a number of days from a given start date, then another which converts back to a date. Once the date is expressed as a number of days, it's trivial to add or subtract to it.

You can find the algorithms here: http://alcor.concordia.ca/~gpkatch/gdate-algorithm.html

How to subtract X day from a Date object in Java?

Java 8 and later

With Java 8's date time API change, Use LocalDate

LocalDate date = LocalDate.now().minusDays(300);

Similarly you can have

LocalDate date = someLocalDateInstance.minusDays(300);

Refer to https://stackoverflow.com/a/23885950/260990 for translation between java.util.Date <--> java.time.LocalDateTime

Date in = new Date();
LocalDateTime ldt = LocalDateTime.ofInstant(in.toInstant(), ZoneId.systemDefault());
Date out = Date.from(ldt.atZone(ZoneId.systemDefault()).toInstant());

Java 7 and earlier

Use Calendar's add() method

Calendar cal = Calendar.getInstance();
cal.setTime(dateInstance);
cal.add(Calendar.DATE, -30);
Date dateBefore30Days = cal.getTime();

Subtract days from a DateTime

That error usually occurs when you try to subtract an interval from DateTime.MinValue or you want to add something to DateTime.MaxValue (or you try to instantiate a date outside this min-max interval). Are you sure you're not assigning MinValue somewhere?

Python - Add OR Subtract N Business Days from Date Input

Seems like a small tweak to your routine would do the trick:

from datetime import datetime, timedelta

def bizday_calc_func(self, start_date, num_days):
    my_start_date = start_date
    my_num_days = abs(num_days)
    inc = 1 if num_days > 0 else -1
    while my_num_days > 0:
      my_start_date += timedelta(days=inc)
      weekday = my_start_date.weekday()
      if weekday >= 5:
        continue
      my_num_days -= 1
    return my_start_date

disclaimer: untested.

Finding date by subtracting X number of days from a particular date in Javascript

Simply:

yourDate.setDate(yourDate.getDate() - daysToSubtract);

How to subtract X days from a date using Java calendar?

Taken from the docs here:

Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling:
Calendar calendar = Calendar.getInstance(); // this would default to now
calendar.add(Calendar.DAY_OF_MONTH, -5).

How to Subtract/Add Days From/To a Date