Welcome to Zoltar 4.1

Zoltar version 4.1 upgrades Zoltar's forecast versioning to support datetime versions rather than date ones. This allows multiple versions for a particular date, as requested by users.

Forecast versioning

Recall that the version of Zoltar prior to this new one added support for storing forecast versions. From the new Forecast Versions page:

Forecasts in Zoltar can be versioned. A version is identified by the combination of the forecast's model, time zero, and issued_at fields. Multiple versions for the same model and time zero will have different issued_at values. These can be identified by the gray version numbering shown in the version column on the model detail page's Forecasts list (e.g., "1 of 2"), and on the Issued at row of the forecast detail page's information table at the top (e.g., "(Version 3 of 3)").

Data migration

This upgrade required migrating existing forecasts' issue_date dates to issued_at timezone-aware datetimes. We arbitrarily chose 12 noon UTC as the time of day.