How Convert Decimal to Posix Time

How convert decimal to POSIX time

@Arun's strategy works, but it might be easier to just do:

x <- c(6.49055593325792, 18.2873900837081)
today<-as.POSIXct('2012-01-23 00:00:00 EST')
today + (3600*x)

# "2012-01-23 06:29:26 EST" "2012-01-23 18:17:14 EST"

That will get you the seconds as well.

Convert a decimal time representation to unix epoch

My C is a bit rusty, but looking at the other two answers I would write a function as follows, returning the number of seconds since epoch or -1 in case of error.

#include <stdio.h>
#include <time.h>

time_t convertDecimalTime(long dt) {
  struct tm time_str;

  time_str.tm_isdst = -1;
  time_str.tm_sec   = dt%100; dt/=100;
  time_str.tm_min   = dt%100; dt/=100;
  time_str.tm_hour  = dt%100; dt/=100;
  time_str.tm_mday  = dt%100; dt/=100;
  time_str.tm_mon   = dt%100-1; dt/=100;
  time_str.tm_year  = dt%10000 - 1900;

  return mktime(&time_str);
}

Converting combined Day/Time decimal format to POSIX

You can use as.POSIXct() to do so:

as.POSIXct.numeric((df$decimal.day-1)*24*3600, 
                   origin=paste(df$Year, df$month, 1, sep = "/"), tz="GMT")

Note the -1 to balance starting the first day of the month

How to convert decimal time to time format

Another option:

library(lubridate)
video$video_duration <- as.numeric(video_end - video_begin, units = "secs")
video$video_duration  <- seconds_to_period(video$video_duration)

          video_begin           video_end video_duration
1 2017-09-12 00:08:14 2017-09-12 00:39:08        30M 54S
2 2017-09-12 00:04:47 2017-09-12 00:47:10        42M 23S
3 2017-09-12 00:08:27 2017-09-12 00:49:51        41M 24S
4 2017-09-12 00:04:59 2017-09-12 00:44:31        39M 32S
5 2017-09-12 00:04:57 2017-09-12 00:39:41        34M 44S
6 2017-09-12 00:07:51 2017-09-12 00:47:12        39M 21S
7 2017-09-12 00:06:11 2017-09-12 00:40:13         34M 2S
8 2017-09-12 00:05:30 2017-09-12 00:46:52        41M 22S

Convert decimal day to HH:MM

Try this:

R> format(as.POSIXct(Sys.Date() + 0.8541667), "%H:%M", tz="UTC")
[1] "20:30"
R> 

We start with a date--which can be any date, so we use today--and add your desired fractional day.

We then convert the Date type into a Datetime object.

Finally, we format the hour and minute part of the Datetime object, ensuring that UTC is used for the timezone.

Converting a day decimal number array to unix timestamp in Python

assuming these numbers are fractional days of the year (UTC) and the year is 2017, in Python you would do

from datetime import datetime, timedelta, timezone

year = datetime(2017,1,1, tzinfo=timezone.utc) # the starting point
doy = [279.341, 279.345, 279.348]

# add days to starting point as timedelta and call timestamp() method:
unix_t = [(year+timedelta(d)).timestamp() for d in doy]
# [1507363862.4, 1507364208.0, 1507364467.2]

Cast decimal number to datetime in Pandas

Here's what ended up working:

posBirch['TimeStamp'] = pd.to_datetime(posBirch['timestep_time'], unit='s')

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