static char *strdelta(int delta, char *buf, int compact) {
  *buf = '\0';
  const char *tail = delta < 0 ? "ago" : "from now";
  struct { const char *fmt; int div; } tab[] = {
    { "%d day%s ", 86400 },
    { "%d hour%s ", 3600 },
    { "%d minute%s ", 60 },
    { "%d second%s ", 1 },
    { NULL, 0 }
  };
  int i;
  delta = abs(delta);
  int sigfigs = 0;
  for (i = 0; tab[i].fmt; i++) {
    int res = (i > 0 ? (delta % tab[i - 1].div) : delta) / tab[i].div;
    if (res == 0 && sigfigs == 0) continue;
    sigfigs++;
    if (delta >= tab[i].div && sigfigs < 2) {
      sprintf(buf + strlen(buf), tab[i].fmt, res, res != 1 ? "s" : "");
      if (compact) break;
    }
  }
  if (*buf) {
    strcat(buf, tail);
  } else {
    strcpy(buf, "now");
  }
  return buf;
}