Spring ahead: Daylight saving time begins March 12

Daylight saving time takes effect on March 12, 2023. Market participants will need to make adjustments in working with market applications for that day.

To accommodate the forward time change, the eMarket application, where bids and offers are submitted, will have no Hour 02 (HOUR ENDING 03) on Sunday, March 12. The Settlement Management System (SMS), used for internal transactions and meter readings, will have no Hour Ending 02. The New England External Transaction Tool (NEXTT), used for external transactions, will have no Hour 02 (HOUR ENDING 03), thus energy intervals for the second hour of the short day should have a start date of 01:00 and a stop date of 03:00 in local time.

For the March 12 operating day, customers who upload files to these applications should not include those hours or they will receive an error message. This issue does not exist for customers who use the user interfaces because those hours will not be available for data entry.

The following table shows how to submit external transactions in the NEXTT and in the NERC eTag systems when the megawatt (MW) profile or price varies over the time change.

NEXTT Schedule (MUI or XML)	Tag Entry (ED Time Zone)
Start-Stop Interval 1 00:00–01:00	01:00–02:00
Start-Stop Interval 2 01:00–03:00	02:00–03:00
Start-Stop Interval 3 03:00–24:00	03:00–24:00

If the megawatt or price change values are constant, the following should be entered:

NEXTT Schedule (MUI or XML)	Tag Entry (ED Time Zone)
Start-Stop Interval 00:00–24:00	01:00–24:00

The Settlements MIS reports will have no hour ending 02 on the short day. Where the trading interval is specified in reports that have five-minute detail, the short day removes intervals from 01:00 to 01:55. For additional information on the MIS reports, please refer to the MIS report descriptions.

All CSV reports and data displays on the public website will have data missing for the hour ending 03 (instead of 02) on the short day. If using web services, interval timestamps rely on the GMT offset to distinguish the trading intervals.

If you have difficulty obtaining approved status while submitting external transactions, call the Tariff, Schedules, and Oasis (TSO) Administrators at (413) 540-4240.

For additional information, please see the file format descriptions on the ISO New England website. If you have questions regarding the change to daylight saving time, please contact Participant Support at (413) 540-4220 or email AskISO@iso-ne.com.