Converting timestamp from TDMS LabView

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Hany Ferdinando
Hany Ferdinando 2025 年 1 月 29 日
コメント済み: Star Strider 2025 年 1 月 30 日
I received measurement data using LabView as a TDMS file and use TDMS reader from https://se.mathworks.com/matlabcentral/fileexchange/30023-tdms-reader to import it. The file name itself already indicated date and time of the measurement, e.g., COP_meas1_25-01-27_1237.tdms, but the resolution was only 1 s.
Using excel with AddOn from NI, I got the following results:
From values attached to this question.
Using
datetime(timestamp(1:5),'ConvertFrom','datenum','TicksPerSecond',1e4,'Format','HH:mm:ss.SSSS')
I got the following results.
05:37:04.1507
05:37:04.1520
05:37:04.1532
05:37:04.1545
05:37:04.1557
Using
datetime(timestamp(1),'ConvertFrom','posixtime')
I got
09-Jan-1970 13:27:24
I have tried using various combinations but I failed. How should I use the parameters to get the same results as in Excel?

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Star Strider
Star Strider 2025 年 1 月 29 日
編集済み: Star Strider 2025 年 1 月 29 日
Ran in:
I did not see the .mat file before, although I did look for it.
Try this —
LD = load('timestamp.mat')
LD = struct with fields:
timestamp: [1124000x1 double]
format long
timestamp = LD.timestamp
timestamp = 1124000×1
1.0e+05 * 7.396442340758194 7.396442340758338 7.396442340758482 7.396442340758628 7.396442340758773 7.396442340758917 7.396442340759061 7.396442340759206 7.396442340759351 7.396442340759496
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Time24 = datetime(timestamp, ConvertFrom='datenum', Format='MM/dd/yyyy HH:mm:ss.SSS', TimeZone='+02:00')
Time24 = 1124000x1 datetime array
01/27/2025 05:37:04.150 01/27/2025 05:37:04.152 01/27/2025 05:37:04.153 01/27/2025 05:37:04.154 01/27/2025 05:37:04.155 01/27/2025 05:37:04.157 01/27/2025 05:37:04.158 01/27/2025 05:37:04.159 01/27/2025 05:37:04.160 01/27/2025 05:37:04.162 01/27/2025 05:37:04.163 01/27/2025 05:37:04.164 01/27/2025 05:37:04.165 01/27/2025 05:37:04.167 01/27/2025 05:37:04.168 01/27/2025 05:37:04.169 01/27/2025 05:37:04.170 01/27/2025 05:37:04.172 01/27/2025 05:37:04.173 01/27/2025 05:37:04.174 01/27/2025 05:37:04.175 01/27/2025 05:37:04.177 01/27/2025 05:37:04.178 01/27/2025 05:37:04.179 01/27/2025 05:37:04.180 01/27/2025 05:37:04.182 01/27/2025 05:37:04.183 01/27/2025 05:37:04.184 01/27/2025 05:37:04.185 01/27/2025 05:37:04.187
LastLine24 = Time24(end)
LastLine24 = datetime
01/27/2025 06:00:29.149
TimeAP = datetime(timestamp, ConvertFrom='datenum', Format='MM/dd/yyyy hh:mm:ss.SSS a', TimeZone='+02:00')
TimeAP = 1124000x1 datetime array
01/27/2025 05:37:04.150 AM 01/27/2025 05:37:04.152 AM 01/27/2025 05:37:04.153 AM 01/27/2025 05:37:04.154 AM 01/27/2025 05:37:04.155 AM 01/27/2025 05:37:04.157 AM 01/27/2025 05:37:04.158 AM 01/27/2025 05:37:04.159 AM 01/27/2025 05:37:04.160 AM 01/27/2025 05:37:04.162 AM 01/27/2025 05:37:04.163 AM 01/27/2025 05:37:04.164 AM 01/27/2025 05:37:04.165 AM 01/27/2025 05:37:04.167 AM 01/27/2025 05:37:04.168 AM 01/27/2025 05:37:04.169 AM 01/27/2025 05:37:04.170 AM 01/27/2025 05:37:04.172 AM 01/27/2025 05:37:04.173 AM 01/27/2025 05:37:04.174 AM 01/27/2025 05:37:04.175 AM 01/27/2025 05:37:04.177 AM 01/27/2025 05:37:04.178 AM 01/27/2025 05:37:04.179 AM 01/27/2025 05:37:04.180 AM 01/27/2025 05:37:04.182 AM 01/27/2025 05:37:04.183 AM 01/27/2025 05:37:04.184 AM 01/27/2025 05:37:04.185 AM 01/27/2025 05:37:04.187 AM
LastLineAP = TimeAP(end)
LastLineAP = datetime
01/27/2025 06:00:29.149 AM
I prefer 24-hour time. I posted conversions for both here.
I am not certain what sort of resolution you want (or what the data provide). I have them in µs here. Append more ‘S’ characters to get additional displayed precision.
The Format name-value pair determines how the datetime values are displayed. It keeps full internal precision regardless.
EDIT — (29 Jan 2025 at 13:22)
Adeded timestamp.mat file import and changed the datetime calls to accommodate it.
EDIT — (29 Jan 2025 at 14:42)
Corrected (added) time zone offset, changed seconds resolution from 6 to 3 (µs to ms). .
.
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Hany Ferdinando
Hany Ferdinando 2025 年 1 月 30 日
Thanks, Star! I realy appreciate your effort to help me! I just knew that we can twist the time zone after creating datetime!
Star Strider
Star Strider 2025 年 1 月 30 日
As always, my pleasure!
The solution was defining the TimeZone of the original as 'Z' (or equivalently, 'UTC'), although I thought that was the default. After that, defining the other time zones is straightforward.

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