title: How to create a time variable
body: <p>I have a lot of netCDF files where they created from tif files using python gdal library. 
  I want to merge each of these files in an large nc file, but they don't have a time variable.</p>
  
  <p>I tried the method described <a href="http://dvalts.io/data/modelling/2018/01/16/NetCDF-merging.html" rel="nofollow noreferrer">here</a> but when I'm going to see the timestamps of each band of the resulted large nc file, it is zeros for all the files.</p>
  
  <p>Moreover, the result of <code>ncdump -h name-of-the-file</code> is as following.</p>
  
  <pre><code>netcdf g2_BIOPAR_VCI_201701010000_AFRI_PROBAV_V1.0.h5_trans {
  dimensions:
          lon = 10081 ;
          lat = 8961 ;
  variables:
          char crs ;
                  crs:grid_mapping_name = "latitude_longitude" ;
                  crs:long_name = "CRS definition" ;
                  crs:longitude_of_prime_meridian = 0. ;
                  crs:semi_major_axis = 6378137. ;
                  crs:inverse_flattening = 298.257223563 ;
                  crs:spatial_ref = "GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433],AUTHORITY[\"EPSG\",\"4326\"]]" ;
                  crs:GeoTransform = "-30 0.008927685745461759 0 40 0 -0.008927575047427742 " ;
          double lat(lat) ;
                  lat:standard_name = "latitude" ;
                  lat:long_name = "latitude" ;
                  lat:units = "degrees_north" ;
          double lon(lon) ;
                  lon:standard_name = "longitude" ;
                  lon:long_name = "longitude" ;
                  lon:units = "degrees_east" ;
          byte Band1(lat, lon) ;
                  Band1:long_name = "GDAL Band Number 1" ;
                  Band1:_Unsigned = "true" ;
                  Band1:valid_range = 0s, 255s ;
                  Band1:_FillValue = 0b ;
                  Band1:VCI_CLASS = "DATA" ;
                  Band1:VCI_MISSING_VALUE = 251 ;
                  Band1:VCI_NB_BYTES = "Uint8" ;
                  Band1:VCI_OFFSET = -5 ;
                  Band1:VCI_ORDER_BYTES = 1 ;
                  Band1:VCI_PRODUCT = "VCI" ;
                  Band1:VCI_SCALING_FACTOR = 0.5f ;
                  Band1:grid_mapping = "crs" ;
  
  // global attributes:
                  :GDAL_ARCHIVE_FACILITY = "VITO" ;
                  :GDAL_CENTRE = "VITO" ;
                  :GDAL_ELLIPSOID_NAME = "WGS84" ;
                  :GDAL_GEODATE_NAME = "WGS84" ;
                  :GDAL_INSTRUMENT_ID = "VGT3" ;
                  :GDAL_LAT = 40 ;
                  :GDAL_LONG = -30 ;
                  :GDAL_OTHER = "GLS" ;
                  :GDAL_OVERALL_QUALITY_FLAG = "OK" ;
                  :GDAL_PIXEL_SIZE = "1km" ;
                  :GDAL_PRODUCT = "Mars VCI data" ;
                  :GDAL_PRODUCT_ALGORITHM_VERSION = 1. ;
                  :GDAL_PRODUCT_TIME = "2017-01-12" ;
                  :GDAL_PROJECTION_NAME = "PlateCarree" ;
                  :GDAL_REGION_NAME = "AFRI" ;
                  :GDAL_SATELLITE = "PROBAV" ;
                  :GDAL_TEMPORAL_NOMINAL = "2017-01-01" ;
                  :GDAL_TEMPORAL_START = "2017-01-01" ;
                  :GDAL_TEMPORAL_STOP = "2017-01-10" ;
                  :Conventions = "CF-1.5" ;
                  :GDAL = "GDAL 2.3.3, released 2018/12/14" ;
                  :history = "Mon Feb 24 14:29:37 2020: GDAL CreateCopy( ../2017/20170101/g2_BIOPAR_VCI_201701010000_AFRI_PROBAV_V1.0.h5_trans.nc, ... )" ;
  </code></pre>
  
  <p>What I want to do is to create a time variable, which will be the same as the global variable: GDAL_TEMPORAL_STOP and merge each file in one large nc file. Ideally I prefer to do this in python. I assume there might be some way to copy the <code>global variable:GDAL_TEMPORAL_STOP = "2017-01-10" ;</code> and copy it as time variable for every file, but I couldn't find a way to do it, so this is where I need your help.</p>