{
# calculate hour, minute, and seconds, and days since 1970/1/1
s = $1 % 60; t = int($1/60);
m = t % 60; t = int( t/60);
h = t % 24;
days_from_epoch = int( t/24);
# calculate year
max_calced_year = 1970; # To remember every days on 01/01 from
days_on_Jan1st_from_epoch[1970] = 0; # the Epoch which was calculated once
Y = int(days_from_epoch/365.2425)+1970+1;
if (Y > max_calced_year) {
i = days_on_Jan1st_from_epoch[max_calced_year];
for (j=max_calced_year; j<Y; j++) {
i += (j%4!=0)?365:(j%100!=0)?366:(j%400!=0)?365:366;
days_on_Jan1st_from_epoch[j+1] = i;
}
max_calced_year = Y;
}
for (;;Y--) {
if (days_from_epoch >= days_on_Jan1st_from_epoch[Y]) {
break;
}
}
# calculate month and date
split("31 0 31 30 31 30 31 31 30 31 30 31", days_of_month); # not sure for February yet
days_of_month[2] = (Y%4!=0)?28:(Y%100!=0)?29:(Y%400!=0)?28:29;
D = days_from_epoch - days_on_Jan1st_from_epoch[Y] + 1;
for (M=1; ; M++) {
if (D > days_of_month[M]) {
D -= days_of_month[M];
} else {
break;
}
}
# finally
printf("%04d/%02d/%02d %02d:%02d:%02d\n",Y,M,D,h,m,s);
}
Note that non-ascii characters in the above source code will be escaped (such as \x9f).