added timestamping interface

grum/dictlist/timestamps.py

@@ -0,0 +1,49 @@
+import functools
+from datetime import datetime
+
+
+DEFAULT_NAMES = (
+    "creation",
+    "access",
+    "modification"
+)
+
+
+class Timestamps:
+
+    def __init__(self, names=DEFAULT_NAMES):
+        dt = datetime.now() # make sure all times are identical at the start
+        self.times = {n: Time(dt) for n in names}
+        self.__dict__.update(self.times)
+
+    def max(self):
+        return max(self.times.values())
+
+    def min(self):
+        return min(self.times.values())
+
+    def __repr__(self):
+        return repr(self.times)
+
+
+
+@functools.total_ordering
+class Time:
+
+    def __init__(self, dt=None):
+        self.dt = dt or datetime.now()
+
+    def update(self):
+        self.dt = datetime.now()
+
+    def __repr__(self):
+        return repr(self.dt)
+
+    def __eq__(self, other):
+        return (self.dt == other.dt)
+
+    def __lt__(self, other):
+        return (self.dt < other.dt)
+
+
+