diff --git a/common/hw-time.ads b/common/hw-time.ads
index aeda5ec..5cfa963 100644
--- a/common/hw-time.ads
+++ b/common/hw-time.ads
@@ -18,6 +18,8 @@
 
    type T is private;
 
+   T_First : constant T;
+
    function Now return T
    with
       Volatile_Function,
@@ -71,6 +73,8 @@
 
    type T is new Word64;
 
+   T_First : constant T := T'First;
+
 end HW.Time;
 
 --  vim: set ts=8 sts=3 sw=3 et: