diff --git a/zerver/lib/timezone.py b/zerver/lib/timezone.py
index 98d6628ffa..a7ad6b823c 100644
--- a/zerver/lib/timezone.py
+++ b/zerver/lib/timezone.py
@@ -1,12 +1,9 @@
 import datetime
-from typing import Any, Dict, List, Union
+from typing import Any, Dict, Union
 
 import pytz
 
 
-def get_all_timezones() -> List[str]:
-    return sorted(pytz.all_timezones)
-
 def get_timezone(tz: str) -> pytz.BaseTzInfo:
     return pytz.timezone(tz)
 
diff --git a/zerver/views/registration.py b/zerver/views/registration.py
index 62f62362c7..da84c9ddf2 100644
--- a/zerver/views/registration.py
+++ b/zerver/views/registration.py
@@ -3,6 +3,7 @@ import smtplib
 import urllib
 from typing import Dict, List, Optional
 
+import pytz
 from django.conf import settings
 from django.contrib.auth import authenticate, get_backends
 from django.core import validators
@@ -50,7 +51,6 @@ from zerver.lib.pysa import mark_sanitized
 from zerver.lib.send_email import FromAddress, send_email
 from zerver.lib.sessions import get_expirable_session_var
 from zerver.lib.subdomains import get_subdomain, is_root_domain_available
-from zerver.lib.timezone import get_all_timezones
 from zerver.lib.url_encoding import add_query_to_redirect_url
 from zerver.lib.users import get_accounts_for_email
 from zerver.lib.zephyr import compute_mit_user_fullname
@@ -290,7 +290,7 @@ def accounts_register(request: HttpRequest) -> HttpResponse:
         default_stream_groups = lookup_default_stream_groups(default_stream_group_names, realm)
 
         timezone = ""
-        if 'timezone' in request.POST and request.POST['timezone'] in get_all_timezones():
+        if 'timezone' in request.POST and request.POST['timezone'] in pytz.all_timezones_set:
             timezone = request.POST['timezone']
 
         if 'source_realm' in request.POST and request.POST["source_realm"] != "on":
diff --git a/zerver/views/user_settings.py b/zerver/views/user_settings.py
index d21149707d..1a1196221f 100644
--- a/zerver/views/user_settings.py
+++ b/zerver/views/user_settings.py
@@ -1,5 +1,6 @@
 from typing import Any, Dict, Optional
 
+import pytz
 from django.conf import settings
 from django.contrib.auth import authenticate, update_session_auth_hash
 from django.core.exceptions import ValidationError
@@ -40,7 +41,6 @@ from zerver.lib.rate_limiter import RateLimited
 from zerver.lib.request import JsonableError
 from zerver.lib.response import json_error, json_success
 from zerver.lib.send_email import FromAddress, send_email
-from zerver.lib.timezone import get_all_timezones
 from zerver.lib.upload import upload_avatar_image
 from zerver.lib.validator import check_bool, check_int, check_int_in, check_string, check_string_in
 from zerver.models import UserProfile, avatar_changes_disabled, name_changes_disabled
@@ -158,7 +158,6 @@ def json_change_settings(request: HttpRequest, user_profile: UserProfile,
 
     return json_success(result)
 
-all_timezones = set(get_all_timezones())
 emojiset_choices = {emojiset['key'] for emojiset in UserProfile.emojiset_choices()}
 
 @human_users_only
@@ -179,7 +178,7 @@ def update_display_settings_backend(
             emojiset_choices), default=None),
         demote_inactive_streams: Optional[int]=REQ(validator=check_int_in(
             UserProfile.DEMOTE_STREAMS_CHOICES), default=None),
-        timezone: Optional[str]=REQ(validator=check_string_in(all_timezones),
+        timezone: Optional[str]=REQ(validator=check_string_in(pytz.all_timezones_set),
                                     default=None)) -> HttpResponse:
 
     # We can't use REQ for this widget because