How do I add days to a date?

Count forward from the start date, rolling over into the next month when you run out of days. The calculator above handles the month lengths and leap years for you.

What is 30 days from today?

Set the number of days to 30 and leave the start date as today. Thirty days is about four and a half weeks, not a calendar month, so it rarely lands on the same date next month.

What is 90 days from today?

Pick 90 days above. It works out at just under three months, and lands about 64 working days ahead if weekends are excluded.

How do I count 30 working days?

Switch the count to working days only. Thirty working days is six calendar weeks, so roughly 42 days on the calendar before public holidays.

Why is 30 days not the same as one month?

Months run from 28 to 31 days. A 30-day deadline from 31 January lands on 2 March in a normal year, not on 28 February.

How do I work out a date in the past?

Set the direction to subtract. The same rules apply going backwards, including the leap years.

Does this include public holidays?

No. Working days here means Monday to Friday only. Public holidays vary by country and state, so subtract them yourself if the deadline depends on them.

How many days is a 3 month notice period?

About 91 days, though it depends which months are involved. Notice periods are normally counted in calendar days including weekends.

What day of the week will it be?

The calculator gives you the weekday for the date it lands on, which is usually the reason people are counting in the first place.

Does this calculator save my dates?

No. It runs entirely in your browser and nothing you enter is stored or sent anywhere.

Calculator

Date Calculator

Pick a date, say how many days to add or take off, and get the date you land on. Choose all days for a deadline that counts weekends, or working days only for one that does not.

Start dateDefaults to todayNumber of daysHow many to add or take off

DirectionForwards or backwardsCountEvery day, or working days only

—

Pick a date and a number of days

Day of the week

—

Where it lands

Working days apart

Monday to Friday

Weeks

0 days counted

Reference

Common spans in weeks and months

Sense-check the span before you count it. Each row turns a number of days into weeks, months, and roughly how many of those days are Monday to Friday.

1 to 30 days1 to 30 days written as weeks, months and roughly how many working days.

1 to 30 days written as weeks, months and roughly how many working days.
Span	Weeks	Months	Working days
1 days	0.14	0.03	about 1
2 days	0.29	0.07	about 1
3 days	0.43	0.1	about 2
4 days	0.57	0.13	about 3
5 days	0.71	0.16	about 4
6 days	0.86	0.2	about 4
7 days	1	0.23	about 5
8 days	1.14	0.26	about 6
9 days	1.29	0.3	about 6
10 days	1.43	0.33	about 7
11 days	1.57	0.36	about 8
12 days	1.71	0.39	about 9
13 days	1.86	0.43	about 9
14 days	2	0.46	about 10
15 days	2.14	0.49	about 11
16 days	2.29	0.53	about 11
17 days	2.43	0.56	about 12
18 days	2.57	0.59	about 13
19 days	2.71	0.62	about 14
20 days	2.86	0.66	about 14
21 days	3	0.69	about 15
22 days	3.14	0.72	about 16
23 days	3.29	0.76	about 16
24 days	3.43	0.79	about 17
25 days	3.57	0.82	about 18
26 days	3.71	0.85	about 19
27 days	3.86	0.89	about 19
28 days	4	0.92	about 20
29 days	4.14	0.95	about 21
30 days	4.29	0.99	about 21

31 to 120 days31 to 120 days written as weeks, months and roughly how many working days.

31 to 120 days written as weeks, months and roughly how many working days.
Span	Weeks	Months	Working days
31 days	4.43	1.02	about 22
32 days	4.57	1.05	about 23
33 days	4.71	1.08	about 24
34 days	4.86	1.12	about 24
35 days	5	1.15	about 25
36 days	5.14	1.18	about 26
37 days	5.29	1.22	about 26
38 days	5.43	1.25	about 27
39 days	5.57	1.28	about 28
40 days	5.71	1.31	about 29
41 days	5.86	1.35	about 29
42 days	6	1.38	about 30
43 days	6.14	1.41	about 31
44 days	6.29	1.45	about 31
45 days	6.43	1.48	about 32
46 days	6.57	1.51	about 33
47 days	6.71	1.54	about 34
48 days	6.86	1.58	about 34
49 days	7	1.61	about 35
50 days	7.14	1.64	about 36
51 days	7.29	1.68	about 36
52 days	7.43	1.71	about 37
53 days	7.57	1.74	about 38
54 days	7.71	1.77	about 39
55 days	7.86	1.81	about 39
56 days	8	1.84	about 40
57 days	8.14	1.87	about 41
58 days	8.29	1.91	about 41
59 days	8.43	1.94	about 42
60 days	8.57	1.97	about 43
65 days	9.29	2.14	about 46
70 days	10	2.3	about 50
75 days	10.71	2.46	about 54
80 days	11.43	2.63	about 57
85 days	12.14	2.79	about 61
90 days	12.86	2.96	about 64
100 days	14.29	3.29	about 71
110 days	15.71	3.61	about 79
120 days	17.14	3.94	about 86

121 to 365 days121 to 365 days written as weeks, months and roughly how many working days.

121 to 365 days written as weeks, months and roughly how many working days.
Span	Weeks	Months	Working days
130 days	18.57	4.27	about 93
140 days	20	4.6	about 100
150 days	21.43	4.93	about 107
160 days	22.86	5.26	about 114
180 days	25.71	5.91	about 129
200 days	28.57	6.57	about 143
210 days	30	6.9	about 150
240 days	34.29	7.89	about 171
270 days	38.57	8.87	about 193
300 days	42.86	9.86	about 214
330 days	47.14	10.84	about 236
360 days	51.43	11.83	about 257
365 days	52.14	11.99	about 261

More than a yearMore than a year written as weeks, months and roughly how many working days.

More than a year written as weeks, months and roughly how many working days.
Span	Weeks	Months	Working days
400 days	57.14	13.14	about 286
456 days	65.14	14.98	about 326
500 days	71.43	16.43	about 357
547 days	78.14	17.97	about 391
600 days	85.71	19.71	about 429
730 days	104.29	23.98	about 521
900 days	128.57	29.57	about 643
1,000 days	142.86	32.85	about 714
1,095 days	156.43	35.98	about 782
1,460 days	208.57	47.97	about 1,043
1,825 days	260.71	59.96	about 1,304
3,650 days	521.43	119.92	about 2,607

Counting forward is where the errors are

Adding days to a date sounds trivial until the span crosses a month end. Thirty days from 31 January is 2 March in a normal year and 1 March in a leap year, and almost nobody gets that right on the first try.

The month lengths are the problem: 28, 29, 30 and 31 days in no useful pattern. A hand count has to remember which months are short, and February changes on a rule most people only half remember.

So the safest habit is to count the days and let something else worry about the calendar, which is what the tool above does.

Working days change the answer completely

A 30-day deadline and a 30-working-day deadline are nearly two weeks apart. Thirty working days is six full weeks, so about 42 days on the calendar, and quoting one when a contract meant the other is a real dispute.

The rule of thumb is that working days run at five sevenths of calendar days, so 90 calendar days is about 64 working ones. That is close enough to sanity-check a plan and not close enough to put in a contract.

Public holidays are the part no calculator can settle for you, because they vary by country and by state. Whatever the tool says, subtract your own.

A date is a promise about work

Counting to a delivery date is the easy half. The hard half is knowing whether the work will fit in it, and that only comes from knowing how long similar work actually took.

That is what a record of hours is for. Reports show how many hours past projects really consumed, which turns the next deadline into an estimate instead of a hope.

If you have two dates and want the gap rather than the destination, the date difference calculator does that. For whole months and years, use the date add and subtract calculator.

Answers

Frequently asked questions

Common queries and answers about the date calculator.

How do I add days to a date?: Count forward from the start date, rolling over into the next month when you run out of days. The calculator above handles the month lengths and leap years for you.
What is 30 days from today?: Set the number of days to 30 and leave the start date as today. Thirty days is about four and a half weeks, not a calendar month, so it rarely lands on the same date next month.
What is 90 days from today?: Pick 90 days above. It works out at just under three months, and lands about 64 working days ahead if weekends are excluded.
How do I count 30 working days?: Switch the count to working days only. Thirty working days is six calendar weeks, so roughly 42 days on the calendar before public holidays.
Why is 30 days not the same as one month?: Months run from 28 to 31 days. A 30-day deadline from 31 January lands on 2 March in a normal year, not on 28 February.
How do I work out a date in the past?: Set the direction to subtract. The same rules apply going backwards, including the leap years.
Does this include public holidays?: No. Working days here means Monday to Friday only. Public holidays vary by country and state, so subtract them yourself if the deadline depends on them.
How many days is a 3 month notice period?: About 91 days, though it depends which months are involved. Notice periods are normally counted in calendar days including weekends.
What day of the week will it be?: The calculator gives you the weekday for the date it lands on, which is usually the reason people are counting in the first place.
Does this calculator save my dates?: No. It runs entirely in your browser and nothing you enter is stored or sent anywhere.

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Date Calculator

Common spans in weeks and months

Counting forward is where the errors are

Working days change the answer completely

A date is a promise about work

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Date Add and Subtract Calculator

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Frequently asked questions

Tired of doing this by hand?