Blog Home » Tech Tip: Julian Days Format

Blog Home » Tech Tip: Julian Days Format

Tech Tip: Julian Days Format

Tech Tip: Julian Days Format

Julian Days

Julian Days” is a numerical timestamp format, calculated by Sea-Bird Scientific CTDs as the number of the days since Jan 1 of that year (e.g., noon on Feb 3 = 34.5). While this format is useful, it is usually more convenient to display data in a visual format such as “2020-02-03 12:00:00″. Learn how to convert Julian Days to standard formats using tools like SBEDataProcessing, Excel, and Matlab.

Exporting “Time, Elapsed: Julian Days” from CTD data provides a count of days since Midnight on Jan 1 of that year, as referenced to the CTD’s timestamp. Some examples:

  • Midnight on January 1st: timeJ = 1​
  • Midnight on January 2nd: timeJ = 2​
  • Midnight on February 1st: timeJ = 32​
  • Noon on February 1st: timeJ = 32.5​​

To convert to a standard time format with a deployment starting in 2020​

  • Sea-Bird Data Processing: Use Time conversion in ASCII out​
  • In Excel: 1/1/2020+timeJ-1​
  • In matlab: datenum(2020, 1, 1)-1+timeJ​
  • In Python: d = datetime.date(dyear, 1, 1) + datetime.timedelta(yday – 1)​
  • In R: time1 <- ISOdatetime(year, 1, 1, 0, 0, 0, tz=’UTC’) + (jday – 1)*86400​

However, beware that the timeJ is referenced against the timezone of the instrument which can either be local or UTC​

# start_time = Feb 25 2019 12:00:01 [Instrument’s time stamp, first data scan]​

June 1, 2020

Related Posts

Featured Posts

World Oceans Week at Sea-Bird Scientific: The HyperNAV Program

A New Paradigm for Ocean Color Satellite Calibration The HyperNAV program is part of the NASA PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) Mission, set to launch in 2024. The NASA PACE Mission is an initiative aimed at helping scientists understand how carbon...

World Oceans Week at Sea-Bird Scientific: The Argo Program

At Sea-Bird Scientific, our ultimate goal is to help scientists and researchers better understand our oceans so they can help policy makers make informed decisions about ocean conservation policy, ocean resource utilization, and more, through accurate and quality...

Pride Month 2022

Celebrating and honoring our LGBTQIA+ communities At Sea-Bird Scientific, we are proud to stand with members of the LGBTQIA+ community during Pride Month 2022. This year, you may have noticed we changed our logo on social media to feature a rainbow throughout the...

Secured By miniOrange