Почему синие или голубые самолёты на флайтрадаре

Синий/голубой цвет значит что трекинг самолёта идёт через спутник.

https://www.flightradar24.com/

Why are some aircraft shown as blue on the map?

Aircraft displayed as blue icons are currently being tracked via satellite. Satellites are collecting the ADS-B signals from aircraft and transmitting them to the Flightradar24 network. Space-based ADS-B tracking will be used to supplement our terrestrial receiver network.

https://www.flightradar24.com/faq

Mongodb aggregate: convert date to another timezone

Mongo version 3.6 timezone operator in  dateToString

Mongo version 3.4 DateToString and Add:

project()
.and(DateOperators.DateToString.dateOf(ArithmeticOperators.Add.valueOf(DATE).add(offsetMilliseconds))
.toString("%Y-%m-%d")).as(DATE_DAYS);

"dateDays": {
"$dateToString": {
"format": "%Y-%m-%d",
"date": {
"$add": ["$date", -36000000]
}
}
}

mongodb download 3.6 and 3.4

https://fastdl.mongodb.org/win32/mongodb-win32-x86_64-2008plus-ssl-3.6.14.zip

https://fastdl.mongodb.org/win32/mongodb-win32-x86_64-2008plus-3.4.23.zip

https://www.mongodb.org/dl/win32/