From cf9c057d273399f29eb0b86afa50294ad5d14d6d Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Sat, 19 Mar 2022 21:14:39 -0400
Subject: datetime: Add function to get seconds since Epoch

And use it in main().
---
diff --git a/src/datetime.c b/src/datetime.c
index cbdf6b4..994d3fe 100644
--- a/src/datetime.c
+++ b/src/datetime.c
@@ -102,6 +102,18 @@ static const char *DATETIME_MISC_FMTS_[] = {
 	" %a %b %d %H:%M:%S %Y ",
 };
 
+static struct tm DATETIME_EPOCH_ = {
+	.tm_sec   = 0,
+	.tm_min   = 0,
+	.tm_hour  = 0,
+	.tm_mday  = 1,
+	.tm_mon   = 0,
+	.tm_year  = 70,
+	.tm_wday  = 4,
+	.tm_yday  = 0,
+	.tm_isdst = -1,
+};
+
 static void
 _datetime_reset_tm(struct tm *tm)
 {
@@ -378,3 +390,13 @@ datetime_strftime_misc(const struct tm *tm, char **out, size_t *buf_sz,
 
 	return _datetime_strftime(DATETIME_MISC_FMTS_, tm, out, buf_sz, buf, i);
 }
+
+double
+datetime_diff_epoch(time_t t)
+{
+	time_t epoch;
+
+	epoch = timegm(&DATETIME_EPOCH_);
+
+	return difftime(t, epoch);
+}
diff --git a/src/datetime.h b/src/datetime.h
index 554748b..e225b52 100644
--- a/src/datetime.h
+++ b/src/datetime.h
@@ -37,4 +37,7 @@ int
 datetime_strftime_misc(const struct tm *tm, char **out, size_t *out_sz,
 		char **buf, size_t *i);
 
+double
+datetime_diff_epoch(time_t t);
+
 #endif  /* DATETIME_H_ */
diff --git a/src/main.c b/src/main.c
index 5e1f799..474f662 100644
--- a/src/main.c
+++ b/src/main.c
@@ -57,18 +57,6 @@ static const struct option LONGOPTS_[] = {
 };
 #endif
 
-static struct tm EPOCH_ = {
-	.tm_sec   = 0,
-	.tm_min   = 0,
-	.tm_hour  = 0,
-	.tm_mday  = 1,
-	.tm_mon   = 0,
-	.tm_year  = 70,
-	.tm_wday  = 4,
-	.tm_yday  = 0,
-	.tm_isdst = -1,
-};
-
 static void
 _print_usage(FILE *stream, const char *program_name)
 {
@@ -287,8 +275,7 @@ main(int argc, char * const argv[])
 	free(buf);
 
 	if (dbg == true) {
-		now = timegm(&EPOCH_);
-		dif = difftime(arg, now);
+		dif = datetime_diff_epoch(arg);
 		printf("%" PRId64 "\n", (int64_t) dif);
 		return EXIT_SUCCESS;
 	}
--
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