config: add "inherit" timezone to use system timezone

Adds support for `timezone: inherit` in runner config to use the
system's local timezone instead of specifying an explicit IANA name.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: aster-void

CLAUDE.md

@@ -45,6 +45,9 @@ struct ScheduleConfig { cron: String }
 ## Config Format
 
 ```yaml
+runner:                        # Optional: global settings
+  timezone: Asia/Tokyo         # Optional: IANA name, "inherit" (system), or omit for UTC
+
 jobs:
   <job-id>:                  # Key = ID (used for directories)
     name: "Display Name"     # Optional (defaults to job-id)

README.md

@@ -70,6 +70,7 @@ rollcron https://github.com/ut-code/rollcron
 ```yaml
 runner:                       # Optional: global settings
   timezone: Asia/Tokyo        # Timezone for cron schedules (default: UTC)
+                              # Use "inherit" to use system timezone
 
 jobs:
   <job-id>:                   # Key is the job ID (used for directories)
@@ -93,7 +94,7 @@ Global settings that apply to all jobs:
 
 | Field | Description |
 |-------|-------------|
-| `timezone` | Timezone for cron schedule interpretation (e.g., `Asia/Tokyo`, `America/New_York`) |
+| `timezone` | Timezone for cron schedule interpretation. Use IANA names (e.g., `Asia/Tokyo`, `America/New_York`), `inherit` (system timezone), or omit for UTC |
 
 ### Concurrency
 

src/config.rs

@@ -6,9 +6,17 @@ use std::collections::HashMap;
 use std::str::FromStr;
 use std::time::Duration;
 
+#[derive(Debug, Clone, Default, PartialEq)]
+pub enum TimezoneConfig {
+    #[default]
+    Utc,
+    Inherit,
+    Named(Tz),
+}
+
 #[derive(Debug, Clone, Default)]
 pub struct RunnerConfig {
-    pub timezone: Option<Tz>,
+    pub timezone: TimezoneConfig,
 }
 
 #[derive(Debug, Deserialize, Default)]
@@ -93,12 +101,14 @@ pub fn parse_config(content: &str) -> Result<(RunnerConfig, Vec<Job>)> {
     let config: Config = serde_yaml::from_str(content)
         .map_err(|e| anyhow!("Failed to parse YAML: {}", e))?;
 
-    let timezone = config
-        .runner
-        .timezone
-        .map(|s| s.parse::<Tz>())
-        .transpose()
-        .map_err(|e| anyhow!("Invalid timezone: {}", e))?;
+    let timezone = match config.runner.timezone {
+        None => TimezoneConfig::Utc,
+        Some(s) if s == "inherit" => TimezoneConfig::Inherit,
+        Some(s) => TimezoneConfig::Named(
+            s.parse::<Tz>()
+                .map_err(|e| anyhow!("Invalid timezone '{}': {}", s, e))?,
+        ),
+    };
 
     let runner = RunnerConfig { timezone };
 
@@ -344,7 +354,7 @@ jobs:
     run: echo test
 "#;
         let (runner, _) = parse_config(yaml).unwrap();
-        assert_eq!(runner.timezone, Some(chrono_tz::Asia::Tokyo));
+        assert_eq!(runner.timezone, TimezoneConfig::Named(chrono_tz::Asia::Tokyo));
     }
 
     #[test]
@@ -357,7 +367,22 @@ jobs:
     run: echo test
 "#;
         let (runner, _) = parse_config(yaml).unwrap();
-        assert!(runner.timezone.is_none());
+        assert_eq!(runner.timezone, TimezoneConfig::Utc);
+    }
+
+    #[test]
+    fn parse_timezone_inherit() {
+        let yaml = r#"
+runner:
+  timezone: inherit
+jobs:
+  test:
+    schedule:
+      cron: "* * * * *"
+    run: echo test
+"#;
+        let (runner, _) = parse_config(yaml).unwrap();
+        assert_eq!(runner.timezone, TimezoneConfig::Inherit);
     }
 
     #[test]

src/scheduler.rs

@@ -1,7 +1,7 @@
-use crate::config::{Concurrency, Job, RetryConfig, RunnerConfig};
+use crate::config::{Concurrency, Job, RetryConfig, RunnerConfig, TimezoneConfig};
 use crate::git;
 use anyhow::Result;
-use chrono::{TimeZone, Utc};
+use chrono::{Local, TimeZone, Utc};
 use rand::Rng;
 use std::collections::HashMap;
 use std::path::PathBuf;
@@ -18,9 +18,10 @@ pub async fn run_scheduler(jobs: Vec<Job>, sot_path: PathBuf, runner: RunnerConf
 
     loop {
         for job in &jobs {
-            let is_due = match runner.timezone {
-                Some(tz) => is_job_due(&job.schedule, tz),
-                None => is_job_due(&job.schedule, Utc),
+            let is_due = match &runner.timezone {
+                TimezoneConfig::Utc => is_job_due(&job.schedule, Utc),
+                TimezoneConfig::Inherit => is_job_due(&job.schedule, Local),
+                TimezoneConfig::Named(tz) => is_job_due(&job.schedule, *tz),
             };
 
             if is_due {