diff --git a/common/ASC.Common/Utils/TimeZoneConverter/TimeZoneConverter.cs b/common/ASC.Common/Utils/TimeZoneConverter/TimeZoneConverter.cs
index c8c549b57b6..7a258451c6e 100644
--- a/common/ASC.Common/Utils/TimeZoneConverter/TimeZoneConverter.cs
+++ b/common/ASC.Common/Utils/TimeZoneConverter/TimeZoneConverter.cs
@@ -66,6 +66,18 @@ public string GetTimeZoneDisplayName(TimeZoneInfo tz)
         return displayName;
     }
 
+    public string GetIanaTimeZoneId(TimeZoneInfo timeZone)
+    {
+        if (timeZone.HasIanaId)
+        {
+            return timeZone.Id;
+        }
+
+        return TimeZoneInfo.TryConvertWindowsIdToIanaId(timeZone.Id, out var ianaTimeZoneId)
+            ? ianaTimeZoneId
+            : WindowsTzId2OlsonTzId(timeZone.Id);
+    }
+
     public string OlsonTzId2WindowsTzId(string olsonTimeZoneId, bool defaultIfNoMatch = true)
     {
         var mapZone = GetMapZoneByWindowsTzId(olsonTimeZoneId);
diff --git a/web/ASC.Web.Api/Api/Settings/SettingsController.cs b/web/ASC.Web.Api/Api/Settings/SettingsController.cs
index 06a31322afe..1a576831c3c 100644
--- a/web/ASC.Web.Api/Api/Settings/SettingsController.cs
+++ b/web/ASC.Web.Api/Api/Settings/SettingsController.cs
@@ -183,9 +183,9 @@ public async Task<SettingsDto> GetSettingsAsync(bool? withpassword)
         {
             settings.TrustedDomains = tenant.TrustedDomains;
             settings.TrustedDomainsType = tenant.TrustedDomainsType;
-            var timeZone = tenant.TimeZone;
-            settings.Timezone = _timeZoneConverter.WindowsTzId2OlsonTzId(timeZone);
-            settings.UtcOffset = _timeZoneConverter.GetTimeZone(timeZone).GetUtcOffset(DateTime.UtcNow);
+            var timeZone = _timeZoneConverter.GetTimeZone(tenant.TimeZone);
+            settings.Timezone = _timeZoneConverter.GetIanaTimeZoneId(timeZone);
+            settings.UtcOffset = timeZone.GetUtcOffset(DateTime.UtcNow);
             settings.UtcHoursOffset = settings.UtcOffset.TotalHours;
             settings.OwnerId = tenant.OwnerId;
             settings.NameSchemaId = _customNamingPeople.Current.Id;
@@ -407,7 +407,7 @@ public async Task<List<TimezonesRequestsDto>> GetTimeZonesAsyncAsync()
         {
             listOfTimezones.Add(new TimezonesRequestsDto
             {
-                Id = _timeZoneConverter.WindowsTzId2OlsonTzId(tz.Id),
+                Id = _timeZoneConverter.GetIanaTimeZoneId(tz),
                 DisplayName = _timeZoneConverter.GetTimeZoneDisplayName(tz)
             });
         }