diff --git a/Cargo.lock b/Cargo.lock
index 4adae16..b9907ef 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "aho-corasick"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "android-tzdata"
 version = "0.1.1"
@@ -236,6 +245,12 @@ version = "0.4.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"
 
+[[package]]
+name = "memchr"
+version = "2.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c8640c5d730cb13ebd907d8d04b52f55ac9a2eec55b440c8892f40d56c76c1d"
+
 [[package]]
 name = "num-traits"
 version = "0.2.17"
@@ -269,6 +284,35 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "regex"
+version = "1.10.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c117dbdfde9c8308975b6a18d71f3f385c89461f7b3fb054288ecf2a2058ba4c"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86b83b8b9847f9bf95ef68afb0b8e6cdb80f498442f5179a29fad448fcc1eaea"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "adad44e29e4c806119491a7f06f03de4d1af22c3a680dd47f1e6e179439d1f56"
+
 [[package]]
 name = "ryu"
 version = "1.0.15"
@@ -331,6 +375,7 @@ version = "0.1.0"
 dependencies = [
  "chrono",
  "clap",
+ "regex",
  "serde",
  "serde_yaml",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index f35f8ba..096f691 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,5 +8,6 @@ edition = "2021"
 [dependencies]
 chrono = "0.4.31"
 clap = { version = "4.4.8", features = ["derive"] }
+regex = "1.10.4"
 serde = { version = "1.0.193", features = ["derive"] }
 serde_yaml = "0.9.27"
diff --git a/src/main.rs b/src/main.rs
index 357baa9..7f3d64e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,8 @@ use std::time::{SystemTime, UNIX_EPOCH, Duration};
 use std::ops::{Add, Sub};
 use clap::Parser;
 use chrono::{TimeZone, Local, Timelike};
+use regex::Regex;
+use serde_yaml::from_str;
 
 #[derive(Debug, Parser)]
 struct Flags {
@@ -26,6 +28,9 @@ struct Flags {
    #[arg(short = 'c', long = "clock")]
    clock: bool,
 
+   #[arg(short = 'd', long = "duration")]
+   duration: Option<String>,
+
    #[arg(short = 'v', long = "verbose")]
    verbose: bool,
 
@@ -154,6 +159,63 @@ fn log(f: &String, enabled: &bool, since: &Option<String>, verbose: &bool, preci
    Ok(())
 }
 
+#[cfg(test)]
+mod test_parse {
+   use super::*;
+
+   #[test]
+   fn test_duration() {
+      assert_eq!(0, parse_duration(&None).unwrap());
+      assert_eq!(1, parse_duration(&Some("1s".to_string())).unwrap());
+      assert_eq!(33, parse_duration(&Some("33s".to_string())).unwrap());
+      assert_eq!(666, parse_duration(&Some("666s".to_string())).unwrap());
+      assert_eq!(60, parse_duration(&Some("1m".to_string())).unwrap());
+      assert_eq!(62, parse_duration(&Some("1m2s".to_string())).unwrap());
+      assert_eq!(3600, parse_duration(&Some("1h".to_string())).unwrap());
+      assert_eq!(3723, parse_duration(&Some("1h2m3s".to_string())).unwrap());
+   }
+}
+
+fn parse_duration(d: &Option<String>) -> Result<u64, String> {
+   match d {
+      Some(d) => {
+         let mut sum: u64 = 0;
+         let re = Regex::new(r"^(?<hours>[0-9]+h)?(?<minutes>[0-9]+m)?(?<seconds>[0-9]+s)?$").unwrap();
+         match re.captures(d) {
+            Some(captures) => {
+               match captures.name("seconds") {
+                  Some(n) => {
+                     let n = n.as_str().to_string();
+                     let n = n.trim_end_matches('s');
+                     sum += from_str::<u64>(n).unwrap();
+                  },
+                  None => {},
+               };
+               match captures.name("minutes") {
+                  Some(n) => {
+                     let n = n.as_str().to_string();
+                     let n = n.trim_end_matches('m');
+                     sum += 60 * from_str::<u64>(n).unwrap();
+                  },
+                  None => {},
+               };
+               match captures.name("hours") {
+                  Some(n) => {
+                     let n = n.as_str().to_string();
+                     let n = n.trim_end_matches('h');
+                     sum += 60 * 60 * from_str::<u64>(n).unwrap();
+                  },
+                  None => {},
+               };
+               Ok(sum)
+            },
+            None => Ok(0),
+         }
+      },
+      None => Ok(0),
+   }
+}
+
 fn parse_time(since: &Option<String>) -> Result<SystemTime, String> {
    match since {
       Some(since) => {