Replace naive datetime with timezone aware.

Also clean-up unused imports.

program/admin.py

-# -*- coding: utf-8 -*-
+from datetime import date, datetime, timedelta
 
-from django.core.exceptions import ObjectDoesNotExist
+from django.conf import settings
 from django.contrib import admin
-from django.utils.translation import ugettext_lazy as _
+from django.core.exceptions import ObjectDoesNotExist
 from django.shortcuts import render
-from django.conf import settings
+from django.utils import timezone
+from django.utils.translation import ugettext_lazy as _
 
-from .models import Language, Type, MusicFocus, Category, Topic, FundingCategory, Host, Note, RRule, Schedule, Show, TimeSlot
 from .forms import MusicFocusForm
-
-from datetime import date, datetime, time, timedelta
+from .models import Language, Type, MusicFocus, Category, Topic, FundingCategory, Host, Note, RRule, Schedule, Show, TimeSlot
 
 
 class ActivityFilter(admin.SimpleListFilter):
@@ -24,21 +23,21 @@ class ActivityFilter(admin.SimpleListFilter):
     def queryset(self, request, queryset):
         if self.parameter_name == 'has_timeslots':  # active/inactive Schedules
             if self.value() == 'yes':
-                return queryset.filter(until__gt=datetime.now()).distinct()
+                return queryset.filter(until__gt=timezone.now()).distinct()
             if self.value() == 'no':
-                return queryset.filter(until__lt=datetime.now()).distinct()
+                return queryset.filter(until__lt=timezone.now()).distinct()
 
         if self.parameter_name == 'has_schedules_timeslots':  # active/inactive Shows
             if self.value() == 'yes':
-                return queryset.filter(schedules__until__gt=datetime.now()).distinct()
+                return queryset.filter(schedules__until__gt=timezone.now()).distinct()
             if self.value() == 'no':
-                return queryset.filter(schedules__until__lt=datetime.now()).distinct()
+                return queryset.filter(schedules__until__lt=timezone.now()).distinct()
 
         if self.parameter_name == 'has_shows_schedules_timeslots':  # active/inactive Hosts
             if self.value() == 'yes':
-                return queryset.filter(shows__schedules__until__gt=datetime.now()).distinct()
+                return queryset.filter(shows__schedules__until__gt=timezone.now()).distinct()
             if self.value() == 'no':
-                return queryset.filter(shows__schedules__until__lt=datetime.now()).distinct()
+                return queryset.filter(shows__schedules__until__lt=timezone.now()).distinct()
 
 
 class ActiveSchedulesFilter(ActivityFilter):
@@ -126,8 +125,8 @@ class NoteAdmin(admin.ModelAdmin):
 
 
     def formfield_for_foreignkey(self, db_field, request=None, **kwargs):
-        four_weeks_ago = datetime.now() - timedelta(weeks=4)
-        in_twelve_weeks = datetime.now() + timedelta(weeks=12)
+        four_weeks_ago = timezone.now() - timedelta(weeks=4)
+        in_twelve_weeks = timezone.now() + timedelta(weeks=12)
 
         if db_field.name == 'timeslot':
             # Adding/Editing a note: load timeslots of the user's shows into the dropdown
@@ -399,8 +398,8 @@ class ShowAdmin(admin.ModelAdmin):
                 tstart = datetime.strptime(request.POST.get('ps_save_tstart'), '%H:%M').time()
                 tend = datetime.strptime(request.POST.get('ps_save_tend'), '%H:%M').time()
                 dstart = datetime.strptime(request.POST.get('ps_save_dstart'), '%Y-%m-%d').date()
-                if dstart < datetime.today().date(): # Create or delete upcoming timeslots only
-                    dstart = datetime.today().date()
+                if dstart < timezone.now().date(): # Create or delete upcoming timeslots only
+                    dstart = timezone.now().date()
                 until = datetime.strptime(request.POST.get('ps_save_until'), '%Y-%m-%d').date()
                 is_repetition = request.POST.get('ps_save_is_repetition')
                 automation_id = int(request.POST.get('ps_save_automation_id')) if request.POST.get('ps_save_automation_id') != 'None' else 0
@@ -486,7 +485,7 @@ class ShowAdmin(admin.ModelAdmin):
                     if ts != None:
                         start_end = ts.split(' - ')
                         # Only create upcoming timeslots
-                        if datetime.strptime(start_end[0], "%Y-%m-%d %H:%M:%S") > datetime.today():
+                        if datetime.strptime(start_end[0], "%Y-%m-%d %H:%M:%S") > timezone.now():
                             timeslot_created = TimeSlot.objects.create(schedule=new_schedule, is_repetition=new_schedule.is_repetition, start=start_end[0], end=start_end[1])
 
                             # Link a note to the new timeslot
@@ -584,7 +583,7 @@ class ShowAdmin(admin.ModelAdmin):
                                                    'num_inputs': len(self.timeslots),
                                                    'step': self.step,
                                                    'max_steps': self.max_steps,
-                                                   'now': datetime.now(),
+                                                   'now': timezone.now(),
                                                    'num_collisions': self.num_collisions})