[Python] pandas conert date failed - pd.to_datetime(df['xxx'], format='%Y-%m-%d').dt.date

I am facing one little problem. I am storing some date time data and the data is

#secCode,secName,announcementTitle,announcementId,announcementTime

003816,xxx name,2024report,1222913141,1743004800000


the date time column is clearly string - 1743004800000, so when I try to convert it

df['announcementTime'] = pd.to_datetime(df['announcementTime'], format='%Y-%m-%d').dt.date


I got this error

File "/root/miniconda3/lib/python3.12/site-packages/pandas/core/tools/datetimes.py", line 1072, in to_datetime
values = convert_listlike(arg._values, format)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/root/miniconda3/lib/python3.12/site-packages/pandas/core/tools/datetimes.py", line 435, in _convert_listlike_datetimes
return _array_strptime_with_fallback(arg, name, utc, format, exact, errors)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: time data "1743004800000" doesn't match format "%Y-%m-%d", at position 0. You might want to try:
- passing `format` if your strings have a consistent format;
- passing `format='ISO8601'` if your strings are all ISO8601 but not necessarily in exactly the same format;
- passing `format='mixed'`, and the format will be inferred for each element individually. You might want to use `dayfirst` alongside this.
df['announcementTime'] = pd.to_datetime(df['announcementTime'], format='%Y-%m-%d')
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/root/miniconda3/lib/python3.12/site-packages/pandas/core/tools/datetimes.py", line 1072, in to_datetime

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