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I'm using Google Earth Engine in Python, but I'm guessing this problem is not specific to Python. I want to use ee.Filter.calendarRange on a feature collection. I was successful at using ee.Filter.calendarRange for an image collection from images stored on the server. I think I need to use ee.ImageCollection.getRegion to avoid doing computations on entire images. So, I am taking the output from getRegion and creating features from it that I'd like to do the computations on. The problem is that I don't know how to set feature dates in such a way that can be understood by ee.Filter.calendarRange. I get EEException: Collection.filter: Can't apply calendarRange filter to objects without a timestamp..

I have an example code that creates 10 dates from Jan 1 to Jan 10, 2010 with "data" values from 0-9. I would like to create a feature collection with just the feature from Jan 3.

def make_fts( val ):
    date = start_date.advance( ee.Number( val ), 'day' )
    ft = ee.Feature( None, {'system:time_start': date, 'data': val} )
    return ft

fake_vals = ee.List( [ee.Number( num ) for num in range(10)] )
start_date = ee.Date( '2010-01-01' )
fc = ee.FeatureCollection( fake_vals.map( make_fts ) )
day_ee_num = ee.Number( 3 )
day_filter = ee.Filter.calendarRange( day_ee_num, day_ee_num, 'day_of_month' ) 
day_three_fc = fc.filter( day_filter )
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1 Answer 1

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You need to store the date as an integer in milliseconds since 1970. You can convert it using .millis().

ft = ee.Feature( None, {'system:time_start': date.millis(), 'data': val} )

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  • Thanks for the idea @JonasV. I'm getting the error as before though. It seems to me that dates are already internally stored as Epoch/Unix. E.g. "date = ee.Date( '2010-01-01' ); print(date.getInfo()) gives {'type': 'Date', 'value': 1262304000000}"
    – AF2k15
    Commented Mar 29, 2021 at 15:56
  • I tested your minimum example with my change and it works perfectly. Make sure in your original code, that you only save dates to system:time_start that have been converted with millis(). If my solution doesn't work, there has to be another problem in your original script that is not captured with your minimum example.
    – JonasV
    Commented Mar 29, 2021 at 16:05
  • Indeed. I had a typo. Thanks so much. I think this gets me unstuck.
    – AF2k15
    Commented Mar 29, 2021 at 16:14

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