Wrong one hour offset on the day the hour changes for DST

[pietercolpaert]

Problem

The GTFS generator script doesn't take into account extra hour on day the clocks are put backwards and doesn't take into account 1 hour less on day the clocks are put 1 hour forward

How to replicate

Load the GTFS feed in any system and check the departure and arrival times on the days the hour change from winter → summer time and vice versa.

I used gtfs2lc to generate connections from this GTFS file.

Examples

2016-03-27: Summer hour (UTC+2) on the day the clocks were set 1 hour forward

{"@type":"Connection","departureStop":"http://irail.be/stations/NMBS/008811221","arrivalStop":"http://irail.be/stations/NMBS/008811213",
// Forgot to substract 1 hour as clocks were set forward
"departureTime":{"$date":"2016-03-27T22:47:00.000Z"},
// → localtime: 2016-03-28T00:47 ==> should have been 2016-03-27T23:47
"arrivalTime":{"$date":"2016-03-27T22:50:00.000Z"},"gtfs:trip":"http://irail.be/trips/IC19453391","gtfs:route":"http://irail.be/vehicle/IC1945",
"_id":"http://irail.be/connections/8811221/20160328/IC1945"}

For the next day, the hour is generated correctly, as no 1 hour disappeared from the day. However, now the identifiers for this departure conflict (which is a big problem for the iRail code base)

{"@type":"Connection","departureStop":"http://irail.be/stations/NMBS/008811221","arrivalStop":"http://irail.be/stations/NMBS/008811213",
"departureTime":{"$date":"2016-03-28T21:47:00.000Z"},
// → Correct local departureTime: 2016-03-28T23:47
"arrivalTime":{"$date":"2016-03-28T21:50:00.000Z"},"gtfs:trip":"http://irail.be/trips/IC19453391","gtfs:route":"http://irail.be/vehicle/IC1945",
"_id":"http://irail.be/connections/8811221/20160328/IC1945"}

2016-10-30: Winter hour (UTC+1) on the day the clocks were set 1 hour backward

Correct day on the 29th, on which we are still on summer time (UTC+2):

{"@type":"Connection","departureStop":"http://irail.be/stations/NMBS/008811213","arrivalStop":"http://irail.be/stations/NMBS/008811221",
"departureTime":{"$date":"2016-10-29T22:12:00.000Z"},
// → Correct local time: 2016-10-30T00:12:00.000
"arrivalTime":{"$date":"2016-10-29T22:15:00.000Z"},"gtfs:trip":"http://irail.be/trips/IC192249921","gtfs:route":"http://irail.be/vehicle/IC1922",
"_id":"http://irail.be/connections/8811213/20161030/IC1922"}

However, on the 30th of October, we forgot to add an hour, as the day lasted 1 hour longer:

{"@type":"Connection","departureStop":"http://irail.be/stations/NMBS/008811213","arrivalStop":"http://irail.be/stations/NMBS/008811221",
"departureTime":{"$date":"2016-10-30T22:12:00.000Z"},
// → Wrong local time as the day lasted 1 hour longer: 2016-10-30T23:12 ==> should have been 2016-10-31T00:12
"arrivalTime":{"$date":"2016-10-30T22:15:00.000Z"},"gtfs:trip":"http://irail.be/trips/IC192249921","gtfs:route":"http://irail.be/vehicle/IC1922","_id":"http://irail.be/connections/8811213/20161030/IC1922"}

Suggested solution

When crossing 3 am, we should start adding or subtracting an hour to the hour we found. However, for the schedules between 2 and 3 am on the 30th of October, I'm not sure what actually happens on the website of SNCB. To be checked!

[pietercolpaert]

The fix is easier than I thought as no trains appear to drive after 1:45. We can just say: everything after 3am gets 1 hour added on the last Sunday of October.

1 hour should be subtracted on the last Sunday of March of each year.