convert narr model data time to datevec or datestr

I have a set of model data that has time attributes:

Attributes:
                     units              = 'hours since 1800-1-1 00:00:0.0'
                     long_name          = 'Time'
                     axis               = 'T'
                     standard_name      = 'time'
                     coordinate_defines = 'start'
                     delta_t            = '0000-00-01 00:00:00'
                     actual_range       = [1.74e+06 1.75e+06]
                     avg_period         = '0000-00-01 00:00:00'

When I pull a sample time such as time(1:5) I get:

     1744392
     1744416
     1744440
     1744464
     1744488

When trying to convert to date string using datestr(time(1)) I get: 25-Dec-4775. I try putting in a pivot year of 1800 but still get the same result. What am I doing wrong? The result should be Jan 1st 1999.

[Star Strider]

How are you calculating 'time'?

[Leyon]

I am not calculating time. The time variable was part of the netcdf file with the attributes shown. A copy of the data (68mb) can be downloaded from:

<ftp://ftp.cdc.noaa.gov/Datasets/NARR/Dailies/monolevel/air.sfc.1999.nc>

Answer 1

[dpb]

>> dn1800=datenum(1800,1,1)   % baseline point in Matlab datenum
dn1800 =
    657438
>> datestr(dn1800+1744392/24)   % add that many hours in days...
ans =
01-Jan-1999

The better way...

>> datestr(addtodate(dn1800,1744392,'hour'))
ans =
01-Jan-1999
>>

[Leyon]

Thanks for the assist. Was becoming quite bothersome.

[Leyon]

how would I go about entering a regular date 1999,1,1 and get the datenum 1744392? I tried reversing your process but that doesn't work

Answer 2

[dpb]

Seems ok to me...

>> (datenum(1999,1,1)-dn1800)*24
ans =
   1744392

Convert the days to hours from the reference point.

[Leyon]

Thanks. Guess my algebra is rusty. Been a long day.