example

$ ./ts < ts.c
2016-12-13 14:52:33-0500        #include <stdlib.h>
2016-12-13 14:52:33-0500        #include <stdio.h>
2016-12-13 14:52:33-0500        #include <time.h>
2016-12-13 14:52:33-0500
2016-12-13 14:52:33-0500        int main(void) {
2016-12-13 14:52:33-0500            char c;
2016-12-13 14:52:33-0500            time_t t;
2016-12-13 14:52:33-0500            struct tm *tm;
2016-12-13 14:52:33-0500            char buf[BUFSIZ];
2016-12-13 14:52:33-0500            while ((c = getchar()) != EOF) {
2016-12-13 14:52:33-0500                if (c == '\n') {
2016-12-13 14:52:33-0500                    t = time(NULL);
2016-12-13 14:52:33-0500                    tm = localtime(&t);
2016-12-13 14:52:33-0500                    if (!tm) {
2016-12-13 14:52:33-0500                        perror("localtime");
2016-12-13 14:52:33-0500                        return EXIT_FAILURE;
2016-12-13 14:52:33-0500                    }
2016-12-13 14:52:33-0500                    if (!strftime(buf, BUFSIZ, "%F %T%z%t", tm)) {
2016-12-13 14:52:33-0500                        perror("strftime");
2016-12-13 14:52:33-0500                        return EXIT_FAILURE;
2016-12-13 14:52:33-0500                    }
2016-12-13 14:52:33-0500                    if (fputs(buf, stderr) < 0) {
2016-12-13 14:52:33-0500                        perror("fputs");
2016-12-13 14:52:33-0500                        return EXIT_FAILURE;
2016-12-13 14:52:33-0500                    }
2016-12-13 14:52:33-0500                }
2016-12-13 14:52:33-0500                if (putchar(c) == EOF) {
2016-12-13 14:52:33-0500                    perror("putchar");
2016-12-13 14:52:33-0500                    return EXIT_FAILURE;
2016-12-13 14:52:33-0500                }
2016-12-13 14:52:33-0500            }
2016-12-13 14:52:33-0500            return 0;
2016-12-13 14:52:33-0500        }

ts.c

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

int main(void) {
    char c;
    time_t t;
    struct tm *tm;
    char buf[BUFSIZ];
    while ((c = getchar()) != EOF) {
        if (c == '\n') {
            t = time(NULL);
            tm = localtime(&t);
            if (!tm) {
                perror("localtime");
                return EXIT_FAILURE;
            }
            if (!strftime(buf, BUFSIZ, "%F %T%z%t", tm)) {
                perror("strftime");
                return EXIT_FAILURE;
            }
            if (fputs(buf, stderr) < 0) {
                perror("fputs");
                return EXIT_FAILURE;
            }
        }
        if (putchar(c) == EOF) {
            perror("putchar");
            return EXIT_FAILURE;
        }
    }
    return 0;
}