diff --git a/src/cron/cli.v b/src/cron/cli.v
index 9bdec9a..8e6b0f1 100644
--- a/src/cron/cli.v
+++ b/src/cron/cli.v
@@ -12,6 +12,7 @@ pub:
 	base_image string = 'archlinux:base-devel'
 }
 
+// cmd returns the cli module that handles the cron daemon.
 pub fn cmd() cli.Command {
 	return cli.Command{
 		name: 'cron'
diff --git a/src/cron/cron.v b/src/cron/cron.v
index 2526326..be37ffa 100644
--- a/src/cron/cron.v
+++ b/src/cron/cron.v
@@ -12,6 +12,7 @@ fn (r1 ScheduledBuild) < (r2 ScheduledBuild) bool {
 	return r1.timestamp < r2.timestamp
 }
 
+// cron starts a cron daemon & starts periodically scheduling builds.
 pub fn cron(conf Config) ? {
 	ce := parse_expression('0 3') ?
 	t := time.parse('2002-01-01 00:00:00') ?
diff --git a/src/cron/expression_test.v b/src/cron/expression_test.v
index ce8526b..0be9a64 100644
--- a/src/cron/expression_test.v
+++ b/src/cron/expression_test.v
@@ -25,4 +25,10 @@ fn test_next_simple() ? {
 	util_test_time('0 3', '2002-01-01 04:00:00', '2002-01-02 03:00:00') ?
 
 	util_test_time('0 3/4', '2002-01-01 04:00:00', '2002-01-01 07:00:00') ?
+
+	// Overlap to next month
+	util_test_time('0 3', '2002-11-31 04:00:00', '2002-12-01 03:00:00') ?
+
+	// Overlap to next year
+	util_test_time('0 3', '2002-12-31 04:00:00', '2003-01-01 03:00:00') ?
 }