As for date fields with the following differences...
|min_resolution||second||One of second/minute/hour/day/month/year. Indicates the smallest unit of measure that must be entered to make a value valid. Eg. if "day" so long as there's a year+month+day the hours,seconds and minutes are optional.|
|render_res||day||One of second/minute/hour/day/month/year. If set to "year" then the dates 1998-10-01, 1998-10 and 1998 would all be rendered as "1998". This is not too useful in configuring the field, but can be set as a print option inside citation files. Although it can be handy to store the time right down to the second, you often will just want to render the hours and minutes for day to day use.|
|render_style||long||One of short/long.
If "long" then you'll see "8 September 1998 23:12:11 +01:00".
If "short" then value is rendered as "08 Sep 1998 23:12:11".