Groupdate

The simplest way to group by:

• day
• week
• hour of the day
• and more (complete list below)

:tada: Time zones - including daylight saving time - supported!! the best part

:cake: Get the entire series - the other best part

Supports PostgreSQL, MySQL, MariaDB, SQLite, and Redshift, plus arrays and hashes

:cupid: Goes hand in hand with Chartkick

Installation

Add this line to your application’s Gemfile:

gem "groupdate"

For MySQL and MariaDB, also follow these instructions.

Getting Started

User.group_by_day(:created_at).count
# {
#   Thu, 01 Jan 2026 => 50,
#   Fri, 02 Jan 2026 => 100,
#   Sat, 03 Jan 2026 => 34
# }

Results are returned in ascending order by default, so no need to sort.

You can group by:

• second
• minute
• hour
• day
• week
• month
• quarter
• year

and

• minute_of_hour
• hour_of_day
• day_of_week (Sunday = 0, Monday = 1, etc)
• day_of_month
• day_of_year
• month_of_year

Use it anywhere you can use group. Works with count, sum, minimum, maximum, and average. For median and percentile, check out ActiveMedian.

Time Zones

The default time zone is Time.zone. Change this with:

Groupdate.time_zone = "Pacific Time (US & Canada)"

or

User.group_by_week(:created_at, time_zone: "Pacific Time (US & Canada)").count
# {
#   Sun, 04 Jan 2026 => 70,
#   Sun, 11 Jan 2026 => 54,
#   Sun, 18 Jan 2026 => 80
# }

Time zone objects also work. To see a list of available time zones in Rails, run rake time:zones:all.

Week Start

Weeks start on Sunday by default. Change this with:

Groupdate.week_start = :monday

or

User.group_by_week(:created_at, week_start: :monday).count

Day Start

You can change the hour days start with:

Groupdate.day_start = 2 # 2 am - 2 am

or

User.group_by_day(:created_at, day_start: 2).count

Time Range

To get a specific time range, use:

User.group_by_day(:created_at, range: 2.weeks.ago.midnight..Time.now).count

To expand the range to the start and end of the time period, use:

User.group_by_day(:created_at, range: 2.weeks.ago..Time.now, expand_range: true).count

To get the most recent time periods, use:

User.group_by_week(:created_at, last: 8).count # last 8 weeks

To exclude the current period, use:

User.group_by_week(:created_at, last: 8, current: false).count

Order

You can order in descending order with:

User.group_by_day(:created_at, reverse: true).count

Keys

Keys are returned as date or time objects for the start of the period.

To get keys in a different format, use:

User.group_by_month(:created_at, format: "%b %Y").count
# {
#   "Jan 2026" => 10
#   "Feb 2026" => 12
# }

or

User.group_by_hour_of_day(:created_at, format: "%-l %P").count
# {
#    "12 am" => 15,
#    "1 am"  => 11
#    ...
# }

Takes a String, which is passed to strftime, or a Symbol, which is looked up by I18n.localize in i18n scope 'time.formats', or a Proc. You can pass a locale with the locale option.

Series

The entire series is returned by default. To exclude points without data, use:

User.group_by_day(:created_at, series: false).count

Or change the default value with:

User.group_by_day(:created_at, default_value: "missing").count

Dynamic Grouping

User.group_by_period(:day, :created_at).count

Limit groupings with the permit option.

User.group_by_period(params[:period], :created_at, permit: ["day", "week"]).count

Raises an ArgumentError for unpermitted periods.

Custom Duration

To group by a specific number of minutes or seconds, use:

User.group_by_minute(:created_at, n: 10).count # 10 minutes

Date Columns

If grouping on date columns which don’t need time zone conversion, use:

User.group_by_week(:created_on, time_zone: false).count

Default Scopes

If you use Postgres and have a default scope that uses order, you may get a column must appear in the GROUP BY clause error (just like with Active Record’s group method). Remove the order scope with:

User.unscope(:order).group_by_day(:count).count

Arrays and Hashes

users.group_by_day { |u| u.created_at } # or group_by_day(&:created_at)

Supports the same options as above

users.group_by_day(time_zone: time_zone) { |u| u.created_at }

Get the entire series with:

users.group_by_day(series: true) { |u| u.created_at }

Count

users.group_by_day { |u| u.created_at }.to_h { |k, v| [k, v.count] }

Additional Instructions

For MySQL and MariaDB

Time zone support must be installed on the server.

mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root mysql

You can confirm it worked with:

SELECT CONVERT_TZ(NOW(), '+00:00', 'Pacific/Honolulu');

It should return the time instead of NULL.

History

View the changelog

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features

To get started with development and testing, check out the Contributing Guide.