Rewrite sdate to take strftime strings.

I decided not to attempt to handle %c for locale-dependent
full date strings.

sdate.py

@@ -1,25 +1,40 @@
 import datetime
+import re
 import time
 
 EPOCH = datetime.datetime(
     year=1993,
     month=9,
     day=1,
-    tzinfo=datetime.timezone.utc,
 )
 
-def sdate():
-    (day, hms) = sdate_tuple()
-    return f'1993 September {day} {hms}'
-
-def sdate_tuple():
-    now = datetime.datetime.now(datetime.timezone.utc)
+def strftime(format, tpl=None):
+    now = datetime.datetime.now()
     diff = now - EPOCH
-    day = diff.days + 1
-    (minutes, seconds) = divmod(diff.seconds, 60)
-    (hours, minutes) = divmod(minutes, 60)
-    hms = f'{hours:02}:{minutes:02}:{seconds:02}'
-    return (day, hms)
+
+    day = str(diff.days + 1)
+    day_of_year = str(244 + diff.days)
+
+    changes = {
+        r'%b': 'Sep',
+        r'%B': 'September',
+        r'%d': day,
+        r'%-d': day,
+        r'%j': day_of_year,
+        r'%-j': day_of_year,
+        r'%m': '09',
+        r'%-m': '9',
+        r'%Y': '1993',
+        r'%y': '93',
+    }
+    for (key, value) in changes.items():
+        key = r'(?<!%)' + key
+        format = re.sub(key, value, format)
+
+    if tpl is not None:
+        return time.strftime(format, tpl)
+    else:
+        return time.strftime(format)
 
 if __name__ == '__main__':
-    print(sdate())
+    print(strftime('%Y-%m-%d %H:%M:%S'))