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To prevent ambiguity, the following date formats are permissible.  Short date formats, particularly those that are all-numeric, must comply with ISO ordering which descends from the largest durations to the smallest (e.g., Year, then Month, then Day).  Years must always be expressed in their 4-digit forms (the 2-digit format was officially eliminated almost ubiquitously during the first decade of the year 2000).

• 2013-May-27 (preferred because it's clear even to those who expect a non-standard order)
• 2013-05-27
• 20130527 (particularly useful in database columns if the "Date" datatype isn't supported)
• Monday, May 27th, 2013 (preferred long format)
• Monday, May 27, 2013 (preferred long format)
• May 27th, 2013
• May 27, 2013

We use 24-hour time on all internal documents and communications.  For clients and some other third parties who prefer it, the use of 12-hour time is permitted.  Our time representation standards are as follows:

• 12:34 (preferred; 24-hour time is always assumed)
• 1234 (used on invoices and in some logs; 24-hour time is always assumed)
• 12:34:56 (seconds included; 24-hour time is always assumed)
• 12:34 -0800 (numeric time-zone included; 24-hour time only)
• 12:34 PST (textual time-zone included; 24-hour time only)
• 12:34 AM (the presence of "AM" or "PM" indicates 12-hour time)
• 12:34:56 AM (seconds included; 12-hour time indicated)

The Date and Time may be combined (or grouped) into a single atomic unit by using a space or a slash (e.g., "2013-05-27 12:34:56 -0800" or "2013-05-27/12:34:56").