old_contents: from django.contrib import admin
  
  from . import models
  
  
  @admin.register(models.Package)
  class PackageAdmin(admin.ModelAdmin):
      list_display = ['billing_type', 'duration', 'price']
  
new_contents: from django import forms
  from django.contrib import admin
  from django.utils.translation import ugettext_lazy as _
  
  from timed.forms import DurationInHoursField
  
  from . import models
  
  
  class PackageForm(forms.ModelForm):
      model = models.Package
      duration = DurationInHoursField(
          label=_('Duration in hours'),
          required=True,
      )
  
  
  @admin.register(models.Package)
  class PackageAdmin(admin.ModelAdmin):
      list_display = ['billing_type', 'duration', 'price']
      form = PackageForm
  
subject: Configure duration field on subscription package in hours