add TimeStamp

csst_common/time.py

 import datetime
 
+from astropy import time
+
 
 def now():
     """ Return ISOT8601 format datetime, for time stamps in data products. """
@@ -9,3 +11,16 @@ def now():
 def now_dfs():
     """ Return ISOT8601 format datetime, for DFS usage only. """
     return datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+
+
+class TimeStamp:
+    def __init__(self, file_path=""):
+        self.file_path = file_path
+
+    def truncate(self):
+        with open(self.file_path, 'w') as file:
+            file.truncate(0)
+
+    def punch_in(self):
+        with open(self.file_path, "a+") as f:
+            f.write(f"{time.Time.now().isot}+00:00\n")