JavaScript Date & Time FAQ

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FAQ 1 How do you check if a date is valid?
FAQ 2 How can I calculate the number of days elapsed between two dates?
FAQ 16 How can I compare a date in a string with todays date?
FAQ 29 How can I calculate someone's age in years, months and days?
FAQ 34 How can I display today's date on my home page in the following styles...?
FAQ 50 How do I show a customized message based on the time of day?
FAQ 58 How can I make the lastModified date more readable?
FAQ 99 How can you display how many years, months & days are left until 31/12/1999?
FAQ 147 How do you subtract X hours from a date?
FAQ 170 How do you add a number of months to a date and then format the output?
FAQ 217 How can I calculate the difference between two dates?
FAQ 228 How do you calulate the Julian day number of a date?
FAQ 238 How can I convert a form field value in HH:MM:SS to pure seconds?
FAQ 256 How can I show the documents last modified date in the format: month, date, year, time(GMT)?
FAQ 268 How do I work out the date seven days before a text string mm/dd/yy?
FAQ 281 How can I tell when Daylight Saving is in effect?
FAQ 300 How can I make the lastModified date more presentable and include the time as well?
FAQ 301 Does setYear work correctly if it is given a two-digit year?
FAQ 344 How can I place the date and time that a form was displayed into a hidden form field?
FAQ 368 How can you display how many days are left until 31/12/1999?
FAQ 379 How can I have a popup date selector return dates to different form fields?
FAQ 451 How can I find the day of the week for a given date?
FAQ 468 How can I detect the hour of the day, and then when someone selects a link, they go to either a "day" page or a "night" page?
FAQ 469 How do I get the dates of next seven weeks in advance
FAQ 470 How can I date/time stamp a form field as the form is submitted?
FAQ 504 How do I get the time on the server, and not on the client computer?
FAQ 533 How can I calculate the number of days in the current month?
FAQ 548 How do I validate a start date and an end date so that start is less than end, and that end is before todays date, using the date format dd/mm/yyyy?
FAQ 549 How can I convert a text string: "Wed Aug 26 14:40:45 MET DST 1998." into a Date object?
FAQ 550 Is there a problem with how the MacOS gives up its date/time?
FAQ 571 How can I store the current date in a hidden form field?
FAQ 583 How can I count the time in seconds that a checkbox is really checked?
FAQ 586 How can I show clocks, one showing the current time, and another showing a time 12 hours behind?
FAQ 605 How can I convert a mm/dd/yy date to dd/mm/yy and vice versa?
FAQ 613 How can I automatically calculate the date of the next meeting which is held on the second Thursday of each month?
FAQ 620 How can I warn that a form submission is due after 25 minutes then submit after a further five minutes?
FAQ 626 How can I add two times together, 08:30 and 08:45 and get 17:15?
FAQ 656 How can you write to the document both the Last Modified and a review date, i.e. Last Modified date plus 100 days?
FAQ 658 The lastModified doesn't appear to be Y2K compliant, for example a document amended with a date of 11th of June 2001 will show 01 as the year when using either getDate() or getFullDate(), is there a workaround?
FAQ 702 I have to run my code which uses the Date object on older browser versions, how do I cope with dates greater than 2000?
FAQ 724 How can I display the date in the format weekday, dd, month, year, for example Friday, 11 Dec 1998?
FAQ 785 How do I pass the client's local time to a server side process?
FAQ 807 How can I subtract 12 months from a date in Julian form and decide whether to subtract 365 days or 366 days (when one of the months included in the 12 months is February and contains 29 days)?
FAQ 808 How do I convert a date from YYMMDD to YYYYDDD?
FAQ 814 Is it possible to accept the year, month and activity from a form an then load the relevant index page page from an activity subdirectory within a month subdirectory with a year subdirectory, e.g. 1996/09/running/index.htm?
FAQ 819 How can I calculate how many hours per each month?
FAQ 842 How can I validate a date to be in the format dd/mm/yyyy?
FAQ 851 Can I show clocks indicating time in different parts of the world?
FAQ 855 How do I produce an alert after a certain predetermined time?
FAQ 857 How do I validate a date in the format YYMMDD?
FAQ 914 How can I calculate the week number of the current date?
FAQ 917 How can I count down from 15 seconds and then display an alert message?
FAQ 919 How do I convert a date in milliseconds back to a date string?
FAQ 938 How can I keep two sets of dates, chosen from drop down select boxes a maximum of 17 days apart, if the first date automatically updates the second date to be 17 days past the first date?
FAQ 1009 How can I have a stop watch that can be paused and unpaused?
FAQ 1029 How can I schedule a meeting for the second Tuesday in every other month?
FAQ 1037 Are there any Y2K date issues with JavaScript?
FAQ 1127 How do I calculate the following dates based on todays date : StartOfLastYear, EndOfLastYear, StartofThisYear, EndOfThisYear, StartOfLastMonth, EndofLastMonth, StartofThisMonth, EndofThisMonth, StartofLastWeek, EndofLastWeek, StartofThisWeek, EndOfThisWeek?
FAQ 1130 How can I display all Sunday - Thursday dates in a list for the entire current year?
FAQ 1141 How can I setup a clock with defined alarm times which trigger another event?
FAQ 1142 How do I add a number of days to a date?
FAQ 1203 I've seen timers that countdown in weeks, days, hours, minutes and seconds, but how can I show a single figure that counts down once every second?
FAQ 1204 How can I count down in seconds from the current time to the year 2000?
FAQ 1309 How can I show all the dates between two dates in YYYY-MM-DD format?
FAQ 1349 How can I check that a string contains a date?
FAQ 1430 How can you compare today's date with a date in a string, then respond wether the string date is ahead, the same, or behind today's date?
FAQ 1436 How can I show the number of days, hours and seconds till Y3K?
FAQ 1451 How can I generate a new date for the beginning of the week, ie, generate the date for the Monday, if the date given is the Thursday of that week?
FAQ 1464 How do I convert the number of milliseconds since January 1, 1970, 00:00:00 into its corresponding date (dd/mm/yy format)?
FAQ 1479 How can I have a clock on a webpage that syncs with the Atomic clock?
FAQ 1493 How can I make a drop down list of dates where the list will display dates in the format mm/dd/yy from today to 14 days before only (this is for a time sheet entry process where dates more than 2 weeks old cant be input)?
FAQ 1494 How can I round numbers with the decimal accuracy specify, correctly. When using Math.ceil it rounds always upwards i.e. 123.1234 (3 decimals) rounds to 123.124 although it shoud be 123.123?
FAQ 1512 How can I countdown to the 17th of May - when I graduate?
FAQ 1520 How do I display the current date as selected options in year, month and day select options?
FAQ 1534 How do I use Eastern Standard Time?
FAQ 1536 How do I create a Javascript that if it is before a specific time (for example, 9 am) it will display tomorrow's day but will show the day AFTER tomorrow day if it is after that specific time?
FAQ 1568 How can I find the last day of the month for any given month?
FAQ 1635 Can I prefill a text form field with the current date?
FAQ 1649 How can I show the next seven days in a drop down list?
FAQ 1688 How do I find the number of days in a month (or last day of a month)?
FAQ 1765 How do you check if a date is valid?
FAQ 1773 Given a start date and a number of days can you calculate the end date?