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The date selection date_select widget by default contains years from five years before to five years after the current date.

This is not sufficient for a birth date field.

Default Data Selection

Let’s assume that you used the scaffold generator to generate controller and views; a date field should look like:

Date of birth

<%= date_select 'employee', 'date_of_birth' %>

This date selection is not sufficient (maybe it is if your application is designed for a kindergarten ;).

Set Options

We have to set the start_year and the end_year options.

The start_year should contain a value equal to the current year and decreased by the supposed maximal age; the end_year should contain a value equal to the current year. The current year we can get by calling the following code:

Time.now.year

Solution

A date selection with a correct list of years:

Date of birth

<%= date_select 'employee', 'date_of_birth',
    :start_year => Time.now.year - 100,
    :end_year => Time.now.year %>

Advanced Solution

If you plan to use this on more places, of course you should reduce the amount of a copy&paste code and if there is a requirement to change the boundaries, it should be in one place.

Add the following code to the app/helpers/application_helper.rb file the following lines:

def getBirthDateStart()
  Time.now.year - 100
end

def getBirthDateEnd()
  Time.now.year
end

and change the date selection code to:

Date of birth

<%= date_select 'employee', 'date_of_birth',
    :start_year => getBirthDateStart(),
    :end_year => getBirthDateEnd() %>

That is it :)