[kronolith] windows mktime warning

[Thomas Spellman]

When I try to set an event with no end time using php4.3.1 on windows, i
get the following error:

Warning: mktime() [function.mktime]: Windows does not support negative
values for this function in
C:\Inetpub\wwwroot\horde\kronolith\lib\Event.php on line 749

Warning: Cannot modify header information - headers already sent by
(output started at C:\Inetpub\wwwroot\horde\kronolith\lib\Event.php:749)
in C:\Inetpub\wwwroot\horde\kronolith\addeventaction.php on line 26

The event gets saved as a "no end time" event but the frame only has the
error in it.  I presume the only way to get around this is to shut off
error displaying.  Turning on output buffering (but not
zlib.output_compression) also made the error go away.