Volume Notification on ‘Long’ Clock Change Day: Sunday 29 October 2023

UK time changes on Sunday 29 October 2023 from British Summer Time (BST) to Greenwich Mean Time (GMT)/ Coordinated Universal Time (UTC) at 02:00 (BST). This will result in a ‘long’ day as the clocks go back an hour.

How are Settlement Periods impacted?

On a ‘long’ clock change day, there are 50 Settlement Periods instead of the standard 48. Settlement Periods one to four inclusive on 29 October 2023 will begin as normal at 00:00 (BST), 00:30 (BST), 01:00 (BST) and 01:30 (BST) respectively.

At 02:00 (BST), the clocks will change to GMT so instead of Settlement Period five beginning at 02:00 (BST), Settlement Period five will begin at 01:00 (GMT). Settlement Period six will begin at 01:30 (GMT) and so on until Settlement Period 50 begins at 23:30 (GMT).


Q. What happens if I submit a contract notification which includes both the clock change day and normal days?

A. If you submit a contract notification that includes the clock change day and normal, non-clock change days, Energy Contract Volume Aggregation Agent (ECVAA) default rules apply.

The notified volumes corresponding to Settlement Periods three and four will also be applied to Settlement Periods five and six on the clock change day.

Notified volumes for the remaining Settlement Periods on the clock change day will all be used for the Settlement Period, two Settlement Periods later than the one they were originally notified for.

Q. What happens if I submit a contract notification for the clock change day alone?

A. If you submit a contract notification for the clock change day alone, the Settlement Periods in the contract notification should be numbered from 1 to 50.

Please note that contract notifications for the clock change day alone must contain the correct number of Settlement Periods as no defaulting rules will be applied to these notifications.

Q. Will the content of any of the reports I receive be different?

A. Yes.

The ECVAA Notification Report (ECVAA-I014) report for 29 October 2023 will contain 50 Settlement Periods and will include the effect of any defaulting rules applied to multi-day notifications.

The ECVAA Forward Contract Report (ECVAA-I022) for 30 October 2022 will show a representation of the original notifications submitted.

Further information

For more information, please contact the BSC Service Desk.


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