diff --git a/pyproject.toml b/pyproject.toml
index dcdb8b7..e819ab6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -91,6 +91,7 @@ dependencies = [
     "w3lib",
     "typing-extensions>=4.12.0",
     "StrEnum>=0.4.0",
+    "numpy",
 ]
 dynamic = ["version"]
 
@@ -103,7 +104,6 @@ dev = [
     "tox",
     "build",
     "ruff",
-    "numpy",
 ]
 
 [project.urls]
diff --git a/src/czml3/examples/simple.py b/src/czml3/examples/simple.py
index 46c9fde..453b8f6 100644
--- a/src/czml3/examples/simple.py
+++ b/src/czml3/examples/simple.py
@@ -693,7 +693,7 @@
                     -5993978.3578334,
                     3085604.46208182,
                     -2127529.51573296,
-                    37792.10937600001,
+                    37792.0,
                     -6130101.19290489,
                     3515932.23049969,
                     9264.18885075031,
@@ -1177,7 +1177,7 @@
                     -6161212.76191318,
                     3460356.43482851,
                     -87207.9167899129,
-                    73212.755328,
+                    73212.0,
                     -6154907.45142338,
                     3472367.94593854,
                     7596.60346604248,
@@ -1341,7 +1341,7 @@
                     -6177229.98169397,
                     3320382.63185734,
                     -879217.258095039,
-                    85019.62118399999,
+                    85019.0,
                     -6162999.06701901,
                     3457830.12375349,
                     7561.5554257676,
diff --git a/src/czml3/types.py b/src/czml3/types.py
index 0601e21..de21723 100644
--- a/src/czml3/types.py
+++ b/src/czml3/types.py
@@ -3,6 +3,7 @@
 import sys
 from typing import Any
 
+import numpy as np
 from dateutil.parser import isoparse as parse_iso_date
 from pydantic import (
     Field,
@@ -81,6 +82,8 @@ def check_values(num_points: int, values: list[Any]):
         raise TypeError(
             f"Input values must have either {num_points} or N * {num_points + 1} values, where N is the number of time-tagged samples."
         )
+    if len(values) % (num_points + 1) == 0 and np.any(np.diff(values[::4]) <= 0):
+        raise TypeError("Time values must be increasing.")
 
 
 def check_reference(r):
diff --git a/tests/simple.czml b/tests/simple.czml
index 095f156..6e24b9d 100644
--- a/tests/simple.czml
+++ b/tests/simple.czml
@@ -810,7 +810,7 @@
         36900,-3994146.68251508,1353941.93189576,-5674612.94646658,
         37200,-5258447.49803637,2337295.48282856,-4108116.98999385,
         37500,-5993978.3578334,3085604.46208182,-2127529.51573296,
-        37792.10937600001,-6130101.19290489,3515932.23049969,9264.18885075031,
+        37792.0,-6130101.19290489,3515932.23049969,9264.18885075031,
         37792.10937600001,-6130384.46590958,3515584.20899647,6695.95297313175,
         37800,-6125874.41162028,3522668.06783492,65343.2925253213,
         38100,-5639991.96555162,3604984.9649137,2253983.5554605,
@@ -931,7 +931,7 @@
         72600,-5202391.35629523,2238791.87144665,-4232583.77922341,
         72900,-5983183.28985049,3000731.20227799,-2274741.09719522,
         73200,-6161212.76191318,3460356.43482851,-87207.9167899129,
-        73212.755328,-6154907.45142338,3472367.94593854,7596.60346604248,
+        73212.0,-6154907.45142338,3472367.94593854,7596.60346604248,
         73212.755328,-6154869.70054271,3472314.27813954,7580.8794079691,
         73500,-5717448.81578568,3570745.1629146,2109098.31104496,
         73800,-4696169.83114091,3320482.84120077,4091785.03705666,
@@ -972,7 +972,7 @@
         84300,-4796522.04551855,1896876.29005214,-4836079.84361999,
         84600,-5777706.24779571,2746906.16140639,-3009492.61314694,
         84900,-6177229.98169397,3320382.63185734,-879217.258095039,
-        85019.62118399999,-6162999.06701901,3457830.12375349,7561.5554257676,
+        85019.0,-6162999.06701901,3457830.12375349,7561.5554257676,
         85019.62118399999,-6162974.43645965,3457855.60563033,7854.92641443949,
         85200,-5953637.85681474,3558954.7436216,1340197.97209599,
         85500,-5128782.17352735,3438064.29435161,3423588.54273433,
diff --git a/tests/test_properties.py b/tests/test_properties.py
index c91c61d..2a18569 100644
--- a/tests/test_properties.py
+++ b/tests/test_properties.py
@@ -1648,3 +1648,8 @@ def test_position_list_of_lists_with_bad_references():
                 values=[["1#this"], ["1#this", "2#this"]]
             ),
         )
+
+
+def test_check_increasing_time():
+    with pytest.raises(TypeError):
+        Cartesian3Value(values=[0, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 0, 0, 0])