diff --git a/users/init.sls b/users/init.sls
index 91c945e..d0bad39 100644
--- a/users/init.sls
+++ b/users/init.sls
@@ -113,7 +113,17 @@ users_{{ name }}_user:
     - createhome: False
     {% endif %}
     {% if 'expire' in user -%}
+        {% if grains['kernel'].endswith('BSD') and
+            user['expire'] < 157766400 %}
+        {# 157762800s since epoch equals 01 Jan 1975 00:00:00 UTC #}
+    - expire: {{ user['expire'] * 86400 }}
+        {% elif grains['kernel'] == 'Linux' and
+            user['expire'] > 84006 %}
+        {# 2932896 days since epoch equals 9999-12-31 #}
+    - expire: {{ (user['expire'] / 86400) | int}}
+        {% else %}
     - expire: {{ user['expire'] }}
+        {% endif %}
     {% endif -%}
     - remove_groups: {{ user.get('remove_groups', 'False') }}
     - groups: