implement oldest newest and near methods in the cdx interface class, now cli uses the cdx methods instead of availablity api methods.

waybackpy/utils.py

@@ -2,8 +2,28 @@
 Utility functions and shared variables like DEFAULT_USER_AGENT are here.
 """
 
+from datetime import datetime
+
 from . import __version__
 
 DEFAULT_USER_AGENT: str = (
     f"waybackpy {__version__} - https://github.com/akamhy/waybackpy"
 )
+
+
+def unix_timestamp_to_wayback_timestamp(unix_timestamp: int) -> str:
+    """
+    Converts Unix time to Wayback Machine timestamp, Wayback Machine
+    timestamp format is yyyyMMddhhmmss.
+    """
+    return datetime.utcfromtimestamp(int(unix_timestamp)).strftime("%Y%m%d%H%M%S")
+
+
+def wayback_timestamp(**kwargs: int) -> str:
+    """
+    Prepends zero before the year, month, day, hour and minute so that they
+    are conformable with the YYYYMMDDhhmmss Wayback Machine timestamp format.
+    """
+    return "".join(
+        str(kwargs[key]).zfill(2) for key in ["year", "month", "day", "hour", "minute"]
+    )