char *format_timestamp_relative(char *buf, size_t l, usec_t t);
char *format_timespan(char *buf, size_t l, usec_t t, usec_t accuracy);
char *format_timestamp_relative(char *buf, size_t l, usec_t t);
char *format_timespan(char *buf, size_t l, usec_t t, usec_t accuracy);