% STR = WFDB_timstr(TIME)
%
% Convert time or time interval into string.
%
% TIME: Time, number of samples. If positive it is treated as a time
%   interval; if negative it is treated as elapsed time, and it is converted
%   into a time of day using the base time indicated in the '.hea' file or
%   previously set using WFDB_setbasetime
% STR: Resulting string, in HH:MM:SS format
%
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