Hi,
I have a DateTime column that takes a Date Column date and adds Hours(1) to it. This should give the last sunday in March datetime (i.e 2018-03-26, 01:00:00 for this year). The odd thing is that it shows as 02:00:00. Doesnt do this if I change the month or if I change the Hours(x) to anything else - shows correctly. Just when Hours(1) is used. Any ideas why?
Hi @Francis_Hampden 
!
My guess would be: Daylight Saving Time ? 
Which happened on the 2023-03-26 this year
The table is to create the times for DTS so yes but …
I am adding 1 hour to the date so surely it isn’t a DST thing. My formular, for each year, takes last Sunday in March as a date and then adds one hour to try and create 2023-03-26, 01:00:00. If BST is always going to kick it forward one hour on 01:00:00 how do I create this time? Seems strange behaviour. Can do 2023-03-26, 00:59:00 and presumably 01:01:00 but not the trip point.
Did you test this ?
I’m asking because some ages ago I ran into this while building a table I needed to parse UTC Date/Time according to DST (in my TZ … which is UTC + 2 at the moment)
Well, I can’t create a date/time between 2 in the morning and 3 for the last Sunday of March… 2 is automatically converted into 3, whatever the minutes I chose…
And to me it makes sense, as for example, the Summer DST switch happened this year, from my side of the screen at 2 in the morning on the 2023-03-26 (in my TZ) … meaning that at 2, it’s in fact 3 o’clock in the morning.
The 2 o’clock moment in time simply doesn’t really exist anymore as 2 but as 3 …
So, I guess this would be the same for BST (which corresponds to UTC + 1) … On the last Sunday in March, 1 o’clock in the morning in your TZ is now 2 o’clock in the morning …
Dates, times & date/time are Doc TZ dependant so in the doc where I needed to parse UTC date/time values according to DST I just chose 3 o’clock in the morning because it works whatever the switch is (as for the Summer switch, 2 becomes 3 and for Winter one, 3 becomes 2 )
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