# Proposal Planning Toolkit: Dates Help

This is a help page specific to using Dates online. For more information, please consult the CIAO Dates help page here.

## Convert from Date System

Select the date system to convert from. The Dates GUI supports the following choices:

## Date

Input the date according to the following formats:
• Calendar Date - YYYY Mon DD [HH:MM:SS.SS] where "Mon" is the first three letters of the month name.
The time of day is optional, and each successive field of the time of day is optional; that is, minutes, seconds, and fractional seconds are optional.
• 1997 Sep 01
• 1997 Jul 04 05:00:00.00

• Julian Date - XXXXXXX.XXXXXXXXXX
When entering a Julian Date or Modified Julian Date, you may specify any number of decimal places, but the program truncates to 10 decimal places. Since this is a truncation and not a rounding, you may lose precision at the tenth decimal place. To get the maximum possible precision, you should round the input Julian Date or Modified Julian Date to 10 decimal places.
• 1234567.1234567890
The minimum acceptable input is 1721425.5 which corresponds to 0001 Jan 01 00:00:00.0

• Modified Julian Date - XXXXX.XXXXXXXXXX
When entering a Julian Date or Modified Julian Date, you may specify any number of decimal places, but the program truncates to 10 decimal places. Since this is a truncation and not a rounding, you may lose precision at the tenth decimal place. To get the maximum possible precision, you should round the input Julian Date or Modified Julian Date to 10 decimal places.
• 12345.1234567890
The minimum acceptable input is -678575.0 which corresponds to 0001 Jan 01 00:00:00.0

• Day of Year - YYYYDDD[.DDDD]
Day of Year for Gregorian Calendar Date

• Chandra Time - SSSSSSSS
Seconds since the start of the Chandra clock on January 1, 1998

## Results

Calendar Date, Julian Date, Modified Julian Date, Day of Year, and Chandra Time are displayed.

## Notes

All dates and times are in Coordinated Universal Time (UTC). UTC is exactly:
• Eastern Daylight Time + 4 hours, or
• Eastern Standard Time + 5 hours, or
• Pacific Daylight Time + 7 hours, or
• Pacific Standard Time + 8 hours, or
• Greenwich Mean Time, or
• British Summer Time - 1 hour, etc.

10.6.3 Tuesday, April 24, 2018
The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email: cxchelp@cfa.harvard.edu Smithsonian Institution, Copyright © 1998-2018. All rights reserved.