diff --git a/bmon.c b/bmon.c
index 0a150d1..ef1180b 100644
--- a/bmon.c
+++ b/bmon.c
@@ -8,13 +8,14 @@
 #include <string.h>
 #include <unistd.h>
 #include <signal.h>
+#include <time.h>
 
 const char *bat_base_path = "/sys/class/power_supply/";
 int dead = 0;
 
 void usage (void)
 {
-	printf("usage: bmon [-h] [-w] [-f file] [-t interval]\n");
+	printf("usage: bmon [-wuh] [-f file] [-t interval]\n");
 }
 
 void int_handler (int signum)
@@ -34,10 +35,11 @@ int main (int argc, char *argv[])
 	int wflag = 0;
 	int wait_time = 10;
 	int fflag = 0;
+	int uflag = 0;
 	char ofile_path[256];
 
 	int opc;
-	while ((opc = getopt(argc, argv, "hwf:t:")) != -1) {
+	while ((opc = getopt(argc, argv, "uhwf:t:")) != -1) {
 		switch (opc) {
 		case 'w':
 			wflag = 1;
@@ -48,11 +50,14 @@ int main (int argc, char *argv[])
 			break;
 		case 't':
 			wait_time = atoi(optarg);
-			if (wait_time < 0) {
+			if (wait_time < 1) {
 				usage();
 				exit(1);
 			}
 			break;
+		case 'u':
+			uflag = 1;
+			break;
 		case 'h':
 		default: /* '?' */
 			usage();
@@ -129,7 +134,7 @@ int main (int argc, char *argv[])
 		}
 	}
 
-	long long elapsed_time = 0;
+	long int elapsed_time = 0;
 	char buf[64];
 	for (; !dead ; sleep(wait_time)) {
 		for (int i = 0; i < fp_num; i++) {
@@ -146,13 +151,13 @@ int main (int argc, char *argv[])
 				printf("%s\t", buf);
 		}
 		if (fflag) {
-			fprintf(ofile_ptr, "%lld\n", elapsed_time);
+			fprintf(ofile_ptr, "%ld\n", uflag ? time(NULL) : elapsed_time);
 			if (fflush(ofile_ptr)) {
 			  perror("error writing to file");
 			  dead = 1;
 			}
 		} else {
-			printf("%lld\n", elapsed_time);
+			printf("%ld\n", uflag ? time(NULL) : elapsed_time);
 		}
 		elapsed_time += wait_time;
 	}