diff --git a/public/astronomical_conversions.php b/public/astronomical_conversions.php
index a904527..ccd0846 100644
--- a/public/astronomical_conversions.php
+++ b/public/astronomical_conversions.php
@@ -1021,7 +1021,7 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
     });
 
     const parseUtcDateTime = function (value) {
-        const match = String(value).trim().match(/^(\d{4})-(\d{2})-(\d{2})(?:[ T](\d{2}):(\d{2})(?::(\d{2}))?)?$/);
+        const match = String(value).trim().match(/^(\d{4})-(\d{2})-(\d{2})(?:[ T](\d{2}):(\d{2})(?::(\d{2})(?:[.,](\d{1,3}))?)?)?$/);
         if (!match) {
             return null;
         }
@@ -1032,7 +1032,8 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
         const hour = Number(match[4] || '0');
         const minute = Number(match[5] || '0');
         const second = Number(match[6] || '0');
-        const date = new Date(Date.UTC(year, month - 1, day, hour, minute, second));
+        const millisecond = Number((match[7] || '0').padEnd(3, '0'));
+        const date = new Date(Date.UTC(year, month - 1, day, hour, minute, second, millisecond));
 
         return Number.isNaN(date.getTime()) ? null : date;
     };
@@ -1054,7 +1055,7 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
             date.getUTCSeconds().toString().padStart(2, '0')
         ];
 
-        return parts.join('-') + ' ' + timeParts.join(':');
+        return parts.join('-') + ' ' + timeParts.join(':') + '.' + date.getUTCMilliseconds().toString().padStart(3, '0');
     };
 
     const formatUtcDateTimeGerman = function (date) {
@@ -1074,11 +1075,11 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
             date.getUTCSeconds().toString().padStart(2, '0')
         ];
 
-        return parts.join('.') + ' ' + timeParts.join(':');
+        return parts.join('.') + ' ' + timeParts.join(':') + ',' + date.getUTCMilliseconds().toString().padStart(3, '0');
     };
 
     const parseUtcDateTimeGerman = function (value) {
-        const match = String(value).trim().match(/^(\d{2})\.(\d{2})\.(\d{4})(?:[ ](\d{2}):(\d{2})(?::(\d{2}))?)?$/);
+        const match = String(value).trim().match(/^(\d{2})\.(\d{2})\.(\d{4})(?:[ ](\d{2}):(\d{2})(?::(\d{2})(?:[.,](\d{1,3}))?)?)?$/);
         if (!match) {
             return null;
         }
@@ -1089,7 +1090,8 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
         const hour = Number(match[4] || '0');
         const minute = Number(match[5] || '0');
         const second = Number(match[6] || '0');
-        const date = new Date(Date.UTC(year, month - 1, day, hour, minute, second));
+        const millisecond = Number((match[7] || '0').padEnd(3, '0'));
+        const date = new Date(Date.UTC(year, month - 1, day, hour, minute, second, millisecond));
 
         return Number.isNaN(date.getTime()) ? null : date;
     };
@@ -1101,6 +1103,9 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
 
         isSyncingTimePicker = true;
         timeUtcPicker.setDate(date, false);
+        if (timeUtcPicker.altInput) {
+            timeUtcPicker.altInput.value = formatUtcDateTimeGerman(date);
+        }
         isSyncingTimePicker = false;
     };
 
@@ -1138,14 +1143,14 @@ $timeLocationLongitude = isset($currentLocation['longitude']) && is_numeric($cur
                 updateTimeFrom('utc');
 
                 if (instance.altInput) {
-                    instance.altInput.setAttribute('placeholder', 'TT.MM.JJJJ HH:MM:SS');
+                    instance.altInput.setAttribute('placeholder', 'TT.MM.JJJJ HH:MM:SS,mmm');
                 }
             }
         });
 
         if (timeUtcPicker.altInput) {
             timeUtcPicker.altInput.classList.add('astro-conv-input');
-            timeUtcPicker.altInput.setAttribute('placeholder', 'TT.MM.JJJJ HH:MM:SS');
+            timeUtcPicker.altInput.setAttribute('placeholder', 'TT.MM.JJJJ HH:MM:SS,mmm');
         }
     }
 
diff --git a/public/py/__pycache__/astronomical_conversions.cpython-314.pyc b/public/py/__pycache__/astronomical_conversions.cpython-314.pyc
index a6e945a..9c37d7b 100644
Binary files a/public/py/__pycache__/astronomical_conversions.cpython-314.pyc and b/public/py/__pycache__/astronomical_conversions.cpython-314.pyc differ
diff --git a/public/py/astronomical_conversions.py b/public/py/astronomical_conversions.py
index c36d797..4c7e661 100644
--- a/public/py/astronomical_conversions.py
+++ b/public/py/astronomical_conversions.py
@@ -129,11 +129,13 @@ def format_decimal_german(value: Decimal | float | int | None, *, max_fraction_d
 
 
 def format_utc_datetime(dt_utc: datetime) -> str:
-    return dt_utc.astimezone(timezone.utc).strftime("%Y-%m-%d %H:%M:%S")
+    dt_utc = dt_utc.astimezone(timezone.utc)
+    return dt_utc.strftime("%Y-%m-%d %H:%M:%S") + f".{dt_utc.microsecond // 1000:03d}"
 
 
 def format_german_datetime(dt_utc: datetime) -> str:
-    return dt_utc.astimezone(timezone.utc).strftime("%d.%m.%Y %H:%M:%S")
+    dt_utc = dt_utc.astimezone(timezone.utc)
+    return dt_utc.strftime("%d.%m.%Y %H:%M:%S") + f",{dt_utc.microsecond // 1000:03d}"
 
 
 def format_clock(hours_value: float) -> str:
@@ -161,9 +163,10 @@ def parse_utc_datetime(value: str) -> datetime | None:
     if text == "":
         return None
 
-    for fmt in ("%Y-%m-%d %H:%M:%S", "%Y-%m-%dT%H:%M:%S", "%Y-%m-%d %H:%M", "%Y-%m-%d"):
+    normalized = text.replace(",", ".")
+    for fmt in ("%Y-%m-%d %H:%M:%S.%f", "%Y-%m-%dT%H:%M:%S.%f", "%Y-%m-%d %H:%M:%S", "%Y-%m-%dT%H:%M:%S", "%Y-%m-%d %H:%M", "%Y-%m-%d"):
         try:
-            parsed = datetime.strptime(text, fmt)
+            parsed = datetime.strptime(normalized, fmt)
             return parsed.replace(tzinfo=timezone.utc)
         except ValueError:
             continue