Convert Unix Time in Date Time Format with Milliseconds

Hello,

i want to convert Unix Time Stamp like this 1545390864126080000 (1.545^18) in a Format like this "Friday, 21. December 2018 11:14:24.126".

I use:

date_time = datestr(unix_time_pose./86400 + datenum(1970,1,1));

unix_time_pose vector is Unix_Time/10^9 and i get something like this '21-Dec-2018 12:04:58'. It is the right date without milliseconds.

Can anyone help me how to get milliseconds,too?

[James Tursa]

What does this show:

whos unix_time_pose

[Sarah Maag]

I have a mobile robot. I get the pose from the odometry of the robot. i only named the vector with the unix time stamps unix_time_pose. Each entry of the vector unix_time_pose has the format unix_time/10⁹ (like 1.545^9) because I divided 1.545^18/10⁹.

Answer 1

[Peter Perkins]

What you have is 1ns ticks since 1970. That's sort of Posix time, but at a different resolution. If that's really what you have, you are gonna need to store the raw numbers as a uint64 array, double will not give you enough precision. So

>> t = uint64(1545390864126080000)
t =
  uint64
   1545390864126080000
>> d = datetime(t,'ConvertFrom','epochtime','TicksPerSecond',1e9,'Format','dd-MMM-yyyy HH:mm:ss.SSSSSSSSS')
d = 
  datetime
   21-Dec-2018 11:14:24.126080000

If you don't care about anything smaller than ms, then you can use double.

>> t = 1545390864126
t =
             1545390864126
>> d = datetime(t,'ConvertFrom','epochtime','TicksPerSecond',1e3,'Format','dd-MMM-yyyy HH:mm:ss.SSS')
d = 
  datetime
   21-Dec-2018 11:14:24.126

[Sarah Maag]

I get this from matlab when I use your code for d.

Error using datetime (line 517)

Invalid parameter name: TicksPerSecond.

[Walter Roberson]

which matlab release are you using ?

[Sarah Maag]

R2018a

[Sarah Maag]

I updated my Software and installed more packages. Now it works. Thanks a lot.

[Taichi Kurayama]

Thank you so much!

Answer 2

[eldar]

If you are reading data in unix timestamp from a .CSV file with a floating point as milliseconds what worked for me was,

dt = datetime(1970,1,1,'Format','dd-MMM-yyyy HH:mm:ss.SSS') + tableData.UnixTime/86400;

[Peter Perkins]

Eldar, this works, but you will likely be happier using the much simpler

datetime(unixTime,"ConvertFrom","posixtime")

[eldar]

Hi Peter, I tried that at first but for some reason did not get the precession that was needed.

[Peter Perkins]

I don't know what that means, but surely if you are converting from seconds to days (using UnixTime/86400) you will be introducing unnecessary noise into your calculations, even if very small.