diff --git a/imap_processing/mag/constants.py b/imap_processing/mag/constants.py
index 8def1f80cd..84b78e63cf 100644
--- a/imap_processing/mag/constants.py
+++ b/imap_processing/mag/constants.py
@@ -2,8 +2,6 @@
 
 from enum import Enum
 
-import numpy as np
-
 
 class DataMode(Enum):
     """
@@ -127,7 +125,7 @@ class ModeFlags(Enum):
     165580141,
 ]
 
-MAX_FINE_TIME = np.iinfo(np.uint16).max  # maximum 16 bit unsigned int
+MAX_FINE_TIME = 65536  # maximum 16 bit unsigned int
 AXIS_COUNT = 3
 RANGE_BIT_WIDTH = 2
 MAX_COMPRESSED_VECTOR_BITS = 60
diff --git a/imap_processing/mag/l1a/mag_l1a_data.py b/imap_processing/mag/l1a/mag_l1a_data.py
index ca360490fc..4bc02428af 100644
--- a/imap_processing/mag/l1a/mag_l1a_data.py
+++ b/imap_processing/mag/l1a/mag_l1a_data.py
@@ -90,9 +90,7 @@ def to_j2000ns(self) -> np.int64:
         j2000ns : numpy.int64
             Time in nanoseconds since J2000 epoch.
         """
-        coarse_j2000ns = np.int64(met_to_ttj2000ns(self.coarse_time))
-        fine_ns = np.int64(self.fine_time / MAX_FINE_TIME * 1e9)
-        return coarse_j2000ns + fine_ns
+        return np.int64(met_to_ttj2000ns(self.to_seconds()))
 
 
 @dataclass
diff --git a/imap_processing/tests/mag/test_mag_l1a.py b/imap_processing/tests/mag/test_mag_l1a.py
index 5f35b961d8..1c961ed3ce 100644
--- a/imap_processing/tests/mag/test_mag_l1a.py
+++ b/imap_processing/tests/mag/test_mag_l1a.py
@@ -790,7 +790,7 @@ def test_time_tuple():
 
     test_add = example_time_tuple + (1000 / MAX_FINE_TIME)
 
-    assert test_add == TimeTuple(439067319, 83)
+    assert test_add == TimeTuple(439067319, 82)
 
 
 def test_calculate_vector_time():