Struggling to convert zonedatetime string to date with mongodb shell

Question

I have these mongo documents with date like this: this date is java: ZonedDateTime.now(), but it came into mongo as string:

db.test.insert({"dateString" : "2020-07-24T11:06:53.975+02:00[GMT+02:00]"})

So i want to pull a report, but formatted it to date, so i can do some difference down the pipeline:
tried:

db.test.aggregate([{$project: {date: {"$dateFromString": {"dateString": "$dateString", "format": "yyyy-MM-dd'T'HH:mm:ss", "timezone": "Etc/GMT+2"}}}}])

But i cant seem to get format right:
"errmsg" : "Error parsing date string '2020-07-24T11:06:53.975+02:00[GMT+02:00]'; 0: Format literal not found '2'; 1: Format literal not found '0'; 2: Format literal not found '2'; 3: Format literal not found '0'; 5: Format literal not found '0'; 6: Format literal not found '7'; 8: Format literal not found '2'; 9: Format literal not found '4'; 10: Format literal not found 'T'; 11: Format literal not found '1'; 12: Format literal not found '1'; 13: Format literal not found ':'; 14: Format literal not found '0'; 15: Format literal not found '6'; 16: Format literal not found ':'; 17: Format literal not found '5'; 18: Format literal not found '3'; 19: Format literal not found '.'; 20: Format literal not found '9'; 21: Format literal not found '7'; 22: Format literal not found '5'; 23: Trailing data '+'"

Answer 1

The date operators will not understand custom format, and also it will not understand the offset timezone

• $substr to select only date from 0 to 23 characters
• set timezone to "GMT"

db.test.aggregate([
  {
    $project: {
      date: {
        "$dateFromString": {
          "dateString": {
            "$substr": [ "$dateString", 0, 23 ]
          },
          "timezone": "GMT"
        }
      }
    }
  }
])

Playground