Any Time value is automatically converted from it’s time zone to UTC when is passed to database. This includes both model fields downstreaming to a database and any query parameter of Time class. This means when record is saved it’s created_at field is converted from it’s time zone (for instance Europe/Kyiv) to UTC. This also works when you use time parameters in your queries:

Book.where { _publication_date < Time.local(2021, 10, 10, 20, location: Jennifer::Config.local_time_zone) }
# SELECT books.* FROM books where books.publication_date < '2021-10-10 17:00:00'

To pass time value into database request as-is - use UTC:

Book.where { _publication_date < Time.utc(2021, 10, 10, 20) }

It is important to notice that column values are converted back to application time zone (set by Jennifer::Config.local_time_zone_name=) when are read from a database. So in both cases User.all.pluck(:created_at) and User.first.created_at time object will be converted from UTC to configured time zone.

Local time could be set using:

Jennifer::Config.config do |conf|
  conf.local_time_zone_name = "Etc/GMT+1"

By default is used local time zone.

It is possible to turn off time zone converting logic entirely by setting Jennifer::Config.time_zone_aware_attributes to false. In this case all time objects will be passed to database without converting to UTC (as “wall clock” time). When time is read from a database Jennifer::Config.local_time_zone as time zone.

If only specific column should ignore time converting logic you can specify time_zone_aware: false option for it in model mapping.

class Book < Jennifer::Model::Base
    # ...
    publishing_date: { type: Time, time_zone_aware: false }

It is important to notice that in this case time zone converting will be omitted only when model instance is read from a database or is written to it. In other words Book.all.pluck(:publishing_date) in this case will perform time zone converting.