The timestampflags option was introduced in build 313 and allows you to customize the format in which the date and times are displayed within the on-screen console log, the on-disk console log, and in keyblock log files (simultaneously, not individually). The following text is what the proxyper readme lists for the definition of the values for this parameter.

Please note that that the timestampflags parameter is the combination of two flags (64 or 128) plus one of the exclusive mode options (1 or 2 or 3). The modes are not bitmasks, and as such only one may be picked at any time. That is why "3" is listed as a distinct option, and does not represent the combination of "1" with "2". As such, the following list is the actual enumeration of all valid combinations.

components	sum	description
1	1	Local time, 2 digit year
2	2	Local time, 4 digit year
3	3	Local time, no year
1+128	129	UTC time, 2 digit year
2+128	130	UTC time, 4 digit year
3+128	131	UTC time, no year
1+64+128	193	UTC time, with label, 2 digit year (old style mode)
2+64+128	194	UTC time, with label, 4 digit year
3+64+128	195	UTC time, with label, no year

It is highly recommended that all future log parsing utilities written by 3rd party developers be capable of parsing any of the timestamp formats. Note however, that the "64" flag does not affect log files, only screen display. Additionally, typically it will not be necessary to take timezone into account (just treat all parsed timestamps as being within the localtime zone and then do not display timezone/UTC labels in your output). As such, only 3 different date formats really need to be parsed (2 digit, 4 digit, and no year). Alternatively, if it is the intention that a 3rd party log parser specifically not support the alternate log formats, then the author of the tool should be sure to clearly indicate what timestamp format is recommended for proper use of his parser tool.