MultiScene.blend(blend_function=timeseries) results in incorrect start_time, end_time

[gerritholl]

Describe the bug

When creating a timeseries using MultiScene.blend(blend_function=timeseries), the start_time and end_time attributes of the datasets in the resulting Scene object are incorrect.

To Reproduce

import satpy
import satpy.utils
satpy.utils.debug_on()
import glob

abi_dir = "/data/gholl/cache/fogtools/abi/2020/04/13/"
abi_glob = f"00/C10/OR_ABI-L1b-RadC-M6C*_G16_s2020104*_e*_c*.nc"
abi_files = glob.glob(abi_dir + abi_glob)

ms = satpy.MultiScene.from_files(
        abi_files,
        reader="abi_l1b")
ms.load(["C10"])
print(ms.scenes[0]["C10"].attrs["start_time"], ms.scenes[-1]["C10"].attrs["end_time"])
sc = ms.blend(blend_function=satpy.multiscene.timeseries)
print(sc["C10"].attrs["start_time"], sc["C10"].attrs["end_time"])

Expected behavior

I expect the output for the two print expressions to be identical.

Actual results

The output of the two print expressions is:

2020-04-13 00:01:13.700000 2020-04-13 00:58:52.100000
2020-04-13 00:28:43.700001 2020-04-13 00:31:22.133333

Full output of test run

[DEBUG: 2020-07-29 18:24:57 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:57 : satpy.multiscene] Forcing iteration of generator-like object of Scenes
[DEBUG: 2020-07-29 18:24:57 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:57 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:57 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040001137_e20201040003522_c20201040003595.nc']
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:24:58 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:58 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040006137_e20201040008522_c20201040008591.nc']
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:24:58 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:58 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040011137_e20201040013521_c20201040013597.nc']
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:24:58 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:58 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:58 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040016137_e20201040018521_c20201040018577.nc']
[DEBUG: 2020-07-29 18:24:58 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:24:59 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:24:59 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:59 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040021137_e20201040023521_c20201040024042.nc']
[DEBUG: 2020-07-29 18:24:59 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:24:59 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:24:59 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:59 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040026137_e20201040028522_c20201040029010.nc']
[DEBUG: 2020-07-29 18:24:59 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:24:59 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:24:59 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:24:59 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:24:59 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040031137_e20201040033521_c20201040033599.nc']
[DEBUG: 2020-07-29 18:24:59 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:25:00 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:25:00 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:25:00 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040036137_e20201040038521_c20201040038582.nc']
[DEBUG: 2020-07-29 18:25:00 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:25:00 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:25:00 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:25:00 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040041137_e20201040043521_c20201040044010.nc']
[DEBUG: 2020-07-29 18:25:00 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:25:00 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:25:00 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:25:00 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:25:00 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040046137_e20201040048522_c20201040049015.nc']
[DEBUG: 2020-07-29 18:25:00 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:25:01 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:25:01 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:25:01 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040051137_e20201040053521_c20201040054005.nc']
[DEBUG: 2020-07-29 18:25:01 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:25:01 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
[DEBUG: 2020-07-29 18:25:01 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
[DEBUG: 2020-07-29 18:25:01 : satpy.readers] Reading ['/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/satpy/etc/readers/abi_l1b.yaml', '/home/gholl/checkouts/satpy/satpy/etc/readers/abi_l1b.yaml']
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.yaml_reader] Assigning to abi_l1b: ['/data/gholl/cache/fogtools/abi/2020/04/13/00/C10/OR_ABI-L1b-RadC-M6C10_G16_s20201040056137_e20201040058521_c20201040059013.nc']
[DEBUG: 2020-07-29 18:25:01 : satpy.composites] Looking for composites config file abi.yaml
[DEBUG: 2020-07-29 18:25:01 : satpy.composites] Looking for composites config file visir.yaml
/data/gholl/miniconda3/envs/py38/lib/python3.8/site-packages/pyproj/crs/crs.py:543: UserWarning: You will likely lose important projection information when converting to a PROJ string from another format. See: https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems
  proj_string = self.to_proj4()
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.abi_l1b] Reading in get_dataset C10.
[DEBUG: 2020-07-29 18:25:01 : satpy.readers.abi_l1b] Calibrating to brightness temperatures
2020-04-13 00:01:13.700000 2020-04-13 00:58:52.100000
[DEBUG: 2020-07-29 18:25:01 : satpy.scene] Setting 'PPP_CONFIG_DIR' to '/home/gholl/checkouts/satpy/satpy/etc/'
2020-04-13 00:28:43.700001 2020-04-13 00:31:22.133333

Environment Info:

• OS: Linux
• Satpy Version: 0.22.1.dev129+g1ddbdb3d
• PyResample Version: 1.16.0+5.gb84acad

Additional context
Also tested with #1269 and #1088, the problem is the same.

[djhoese]

Related by @zxdawn #1173 and #1246
And I thought there was another one somewhere for adding better support for start/end time to be the min/max instead of the average (which I think is what's happening here).

[djhoese]

Here it is #1174

[gerritholl]

Oh, right. I didn't see that one, that probably makes this a duplicate as I suppose combine_metadata is used under the hood here.

[djhoese]

Yeah here it is:

satpy/satpy/multiscene.py

Line 71 in 1ddbdb3

res.attrs = combine_metadata(*[x.attrs for x in expanded_ds])

Let's close this as a duplicate of #1174 then.