Calendar date fuzzer
World's simplest time toolWith this browser-based application, you can turn the given list of calendar dates into a similar list with slight date perturbations. You can change a date by a random interval, which is expressed in days, months, years, hours, minutes, and seconds. You can control the fuzziness direction and get a slightly incremented date or a slightly decremented date. The deviation amount is controlled by setting the minimum and maximum fuzziness values in the options. You can also customize the fuzzed date format, change the clock format, and control the date and time component padding. Created by computer nerds from team Browserling.
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What is a calendar date fuzzer?
learn more about this toolThis is a quick online utility for adding fuzziness to a calendar date. When a calendar date is made fuzzy, its value is perturbed and a minor random deviation from its original value is created. The fuzziness can increase or decrease a date by a random number of days, months, years, and optionally hours, minutes, and seconds. This random number is called the fuzziness parameter and it's set by changing the primary fuzziness option. For example, you can specify the fuzziness parameter equal to "2 days", "3 months", "1 year", "1 day 10 hours", or "2 months 10 minutes". Our program accepts multiple dates as the input, entered one per line, in the format "YYYY-MM-DD" or "YYYY-MM-DD hh:mm:ss". For example, you can enter the date "2025-04-10 00:00:00" and perturb it by 1 day. In this case, the perturbation algorithm will first generate a random value from 0 seconds to 1 day (86400 seconds) and then it will increase or decrease the date by this amount. As a result, you'll get dates such as "2025-04-10 12:35:55", "2025-04-09 01:20:24", or "2025-04-11 01:23:10" as the output. To prevent too small date deviations (such as 1 second), you can also specify the minimum fuzzy interval in the options. For example, if we keep 1 day as the initial perturbation value and set the minimum perturbation value to 12 hours, then the program will generate a random value from 12 hours (43200 seconds) to 1 day (86400 seconds), and increase or decrease the date by this larger value. If you always need to only increment a date, you can put a "+" sign in front of the fuzzy value, such as "+1 day", or "+2 months 20 hours". If you always need to only decrement a date, use the "-" sign, such as "-2 years", "-1 month 3 days". In addition to controlling the fuzziness, you can also adjust the fuzzy date format in the output. The date format can use all or some of the date components and they can be put in any order. Also, the names of months and days of the week can be printed as text in both the short and long forms. The most popular date formats are available in the date format list option and you can also create custom and original date formats. To do it, you need to select the custom date format mode from the list and enter a date pattern using the special abbreviations for individual time components. Additionally, you can control the padding of date components via a checkbox option. If your dates have the clock time part, you can adjust the clock format – you can turn all the clocks into a 12-hour format, turn them into a 24-hour format, or keep the original clock format. Timeabulous!
Calendar date fuzzer examples
Click to useCreate Random Date Deviations
In this example, we use our date fuzzer for an astronomical research problem. To create a testing set for a future satellite launch, we need to generate ten calendar dates that are within one day of the date 2030-06-16 12:00:00. We enter this date ten times in the input and set the perturbation option to "1 day", which means – change all dates by any amount that is not bigger than 1 day. As a result, the program picks a random number from 0 (0 days) to 86400 (1 day) and adds or subtracts this number (as seconds) from each input date. We also switch to a new date format and get slash-separated dates in the output.
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030-06-16 12:00:00
2030/06/16 04:47:07
2030/06/16 19:53:01
2030/06/17 02:25:03
2030/06/17 06:11:53
2030/06/15 15:19:23
2030/06/17 09:58:55
2030/06/16 18:15:54
2030/06/17 02:22:18
2030/06/15 12:06:42
2030/06/16 19:02:11
Required options
Maximum date fuzziness value.
Use the "+" sign to only increase
a date.
Use the "-" sign to only decrease
a date.
No sign means to change it
randomly in any direction.
For example, "1day 12hr",
"+5 days", "-3yr 6mo 20hr".
Use the "+" sign to only increase
a date.
Use the "-" sign to only decrease
a date.
No sign means to change it
randomly in any direction.
For example, "1day 12hr",
"+5 days", "-3yr 6mo 20hr".
Minimum date fuzzy interval.
Adjust the format for fuzzed
dates in the output.
dates in the output.
Custom date format constructor.
(To activate, choose the custom
format in the list above.)
(To activate, choose the custom
format in the list above.)
Output fuzzed dates with
padded date and time parts.
padded date and time parts.
Output fuzzed dates with
the original clock format.
the original clock format.
Random Date Increments
This example applies random increments to five calendar dates. It uses a fuzzy value with a plus sign "+2 months", which means that the algorithm creates only positive date deviations and all fuzzed dates are larger than the given dates. The deviations also have a restraint on its minimum value and it's set to "1 month". This restriction makes the program use only values between 1 month and 2 months for fuzzing. For the output, we choose a date format that includes the textual names of the months and days of the week. We also turn off the padding for numerical date components and convert all clock times to a 12-hour am/pm format.
2004-08-04 02:00:00
2027-02-15 12:00:0
2078-08-19 13:00:00
2059-04-28 04:00:00
2072-02-05 04:00:00
Sat, Oct 2, 2004 9:24:27 am
Thu, Apr 15, 2027 1:48:50 am
Thu, Oct 13, 2078 8:36:38 pm
Thu, May 15, 2059 1:23:31 pm
Sun, Mar 13, 2072 8:22:12 am
Required options
Maximum date fuzziness value.
Use the "+" sign to only increase
a date.
Use the "-" sign to only decrease
a date.
No sign means to change it
randomly in any direction.
For example, "1day 12hr",
"+5 days", "-3yr 6mo 20hr".
Use the "+" sign to only increase
a date.
Use the "-" sign to only decrease
a date.
No sign means to change it
randomly in any direction.
For example, "1day 12hr",
"+5 days", "-3yr 6mo 20hr".
Minimum date fuzzy interval.
Adjust the format for fuzzed
dates in the output.
dates in the output.
Custom date format constructor.
(To activate, choose the custom
format in the list above.)
(To activate, choose the custom
format in the list above.)
Output fuzzed dates with
padded date and time parts.
padded date and time parts.
Output fuzzed dates with
the 12-hour clock format.
the 12-hour clock format.
Add 1-year Fuzziness
In this example, we specify the minimum fuzziness value equal to "1 year" and the maximum fuzziness value equal to "1 year 6 months". These min-max interval values increment or decrement each date by at least 1 year, which adds a large amount of fuzziness to the eight input dates from different centuries. We switch to the custom date format mode and create a date template without the time part "MM.DD.YYYY".
1960-09-02
2076-06-21
2090-06-30
1929-04-15
2007-07-03
2061-12-26
1933-06-01
1918-11-22
08.30.1960
03.30.2075
10.08.2089
04.27.1929
11.01.2008
01.21.2063
03.04.1932
03.13.1920
Required options
Maximum date fuzziness value.
Use the "+" sign to only increase
a date.
Use the "-" sign to only decrease
a date.
No sign means to change it
randomly in any direction.
For example, "1day 12hr",
"+5 days", "-3yr 6mo 20hr".
Use the "+" sign to only increase
a date.
Use the "-" sign to only decrease
a date.
No sign means to change it
randomly in any direction.
For example, "1day 12hr",
"+5 days", "-3yr 6mo 20hr".
Minimum date fuzzy interval.
Adjust the format for fuzzed
dates in the output.
dates in the output.
Custom date format constructor.
(To activate, choose the custom
format in the list above.)
(To activate, choose the custom
format in the list above.)
Output fuzzed dates with
padded date and time parts.
padded date and time parts.
Output fuzzed dates with
the original clock format.
the original clock format.
Pro tips Master online time tools
You can pass input to this tool via ?input query argument and it will automatically compute output. Here's how to type it in your browser's address bar. Click to try!
https://onlinetools.com/time/add-fuzziness-to-calendar-dates?input=2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00%0A2030-06-16%2012%3A00%3A00&fuzziness=1%20day&min-fuzzy-interval=&format=YYYY%252FMM%252FDD%20hh%253Amm%253Ass&custom-format=YYYY_MM_DD&padding=true&use-given-clock-format=true
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• MMMM/MMM/MM – month,
• dddd/ddd – day of week,
• DD – day, • hh – hour,
• mm – minute, • ss – second.