diff --git a/changes/1600-mlbiche.md b/changes/1600-mlbiche.md
new file mode 100644
index 0000000000..e58c4f500c
--- /dev/null
+++ b/changes/1600-mlbiche.md
@@ -0,0 +1 @@
+Update datetime parser to support negative timestamps
diff --git a/docs/usage/types.md b/docs/usage/types.md
index a9b2a451b1..67db54fe5c 100644
--- a/docs/usage/types.md
+++ b/docs/usage/types.md
@@ -248,7 +248,7 @@ types:
 * `datetime` fields can be:
 
     * `datetime`, existing `datetime` object
-    * `int` or `float`, assumed as Unix time, i.e. seconds (if <= `2e10`) or milliseconds (if > `2e10`) since 1 January 1970
+    * `int` or `float`, assumed as Unix time, i.e. seconds (if >= `-2e10` or <= `2e10`) or milliseconds (if < `-2e10`or > `2e10`) since 1 January 1970
     * `str`, following formats work:
 
         * `YYYY-MM-DD[T]HH:MM[:SS[.ffffff]][Z[±]HH[:]MM]]]`
diff --git a/pydantic/datetime_parse.py b/pydantic/datetime_parse.py
index 69e7882dfb..1bdc13a3af 100644
--- a/pydantic/datetime_parse.py
+++ b/pydantic/datetime_parse.py
@@ -75,7 +75,7 @@ def get_numeric(value: StrBytesIntFloat, native_expected_type: str) -> Union[Non
 
 
 def from_unix_seconds(seconds: Union[int, float]) -> datetime:
-    while seconds > MS_WATERSHED:
+    while abs(seconds) > MS_WATERSHED:
         seconds /= 1000
     dt = EPOCH + timedelta(seconds=seconds)
     return dt.replace(tzinfo=timezone.utc)
diff --git a/tests/test_datetime_parse.py b/tests/test_datetime_parse.py
index 545a499b57..20cba7b2b0 100644
--- a/tests/test_datetime_parse.py
+++ b/tests/test_datetime_parse.py
@@ -93,6 +93,7 @@ def test_time_parsing(value, result):
         (1_494_012_444, datetime(2017, 5, 5, 19, 27, 24, tzinfo=timezone.utc)),
         # values in ms
         ('1494012444000.883309', datetime(2017, 5, 5, 19, 27, 24, 883, tzinfo=timezone.utc)),
+        ('-1494012444000.883309', datetime(1922, 8, 29, 4, 32, 35, 999117, tzinfo=timezone.utc)),
         (1_494_012_444_000, datetime(2017, 5, 5, 19, 27, 24, tzinfo=timezone.utc)),
         ('2012-04-23T09:15:00', datetime(2012, 4, 23, 9, 15)),
         ('2012-4-9 4:8:16', datetime(2012, 4, 9, 4, 8, 16)),