diff --git a/src/activity.rs b/src/activity.rs
new file mode 100644
index 0000000..2b0768b
--- /dev/null
+++ b/src/activity.rs
@@ -0,0 +1,271 @@
+use chrono::{NaiveDateTime, Local, Duration};
+use std::fmt;
+use std::str::{FromStr, Chars};
+use thiserror::Error;
+
+use crate::project;
+use crate::conf;
+
+#[derive(Debug)]
+pub struct Activity {
+	pub start : NaiveDateTime,
+	pub end : Option<NaiveDateTime>,
+	
+	pub project : project::Project,
+	pub description : String
+}
+
+#[derive(Error,Debug)]
+pub enum ActivityError {
+	#[error("could not parse date or time of activity")]
+	DateTimeParseError,
+	#[error("could not parse activity")]
+	GeneralParseError
+}
+
+impl Activity {
+	pub fn start(project : project::Project, description : String) -> Activity {
+		Activity {
+			start : Local::now().naive_local(),
+			end: None,
+			project,
+			description
+		}
+	}
+	
+	pub fn stop(&mut self) {
+		self.end = Some(Local::now().naive_local());
+	}
+	
+	pub fn is_stopped(&self) -> bool {
+		self.end.is_some()
+	}
+	
+	pub fn get_duration(&self) -> Duration {
+		if let Some(end) = self.end {
+			end.signed_duration_since(self.start)
+		} else {
+			Local::now().naive_local().signed_duration_since(self.start)
+		}
+	}
+}
+
+impl fmt::Display for Activity {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		let escaped_project_name = escape_special_chars(&format!("{}", self.project));
+		let escaped_description = escape_special_chars(&self.description);
+		
+		match self.end {
+			None => writeln!(f, "{} | {} | {}", self.start.format(conf::FORMAT_DATETIME), escaped_project_name, escaped_description),
+			Some(end) => writeln!(f, "{} - {} | {} | {}", self.start.format(conf::FORMAT_DATETIME), end.format(conf::FORMAT_DATETIME), escaped_project_name, escaped_description)
+		}
+	}
+}
+
+// escapes the pipe character, so we can use it to seperate the distinct parts of a activity
+fn escape_special_chars(s: &str) -> String {
+	s.replace("\\", "\\\\").replace("|", "\\|")
+}
+
+impl FromStr for Activity {
+	type Err = ActivityError;
+	
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		let parts : Vec<String> = split_with_escaped_delimeter(s).collect();
+				
+		if parts.len() < 2 {
+			return Err(ActivityError::GeneralParseError);
+		}
+	
+		let time_parts : Vec<&str> = parts[0].split(" - ").collect();
+		
+		let starttime = match NaiveDateTime::parse_from_str(time_parts[0].trim(), conf::FORMAT_DATETIME) {
+			Ok(t) => t,
+			Err(_) => {
+				return Err(ActivityError::DateTimeParseError)
+			}
+		};
+		
+		let endtime: Option<NaiveDateTime>;
+		
+		if time_parts.len() > 1 {
+			endtime = match NaiveDateTime::parse_from_str(time_parts[1].trim(), conf::FORMAT_DATETIME) {
+				Ok(t) => Some(t),
+				Err(_) => {
+					return Err(ActivityError::DateTimeParseError)
+				}
+			}
+		} else {
+			endtime = None;
+		}
+		
+		let project = parts[1].trim();
+		let description = if parts.len() > 2 { parts[2].trim() } else {	"" };
+		
+		let activity = Activity{
+			start: starttime,
+			end: endtime,
+			project: project::Project(project.to_string()),
+			description: description.to_string()
+		};
+		
+		Ok(activity)
+	}
+}
+
+/**
+ * an iterator for splitting strings at the pipe character "|"
+ * 
+ * this iterator splits strings at the pipe character. It ignores all pipe characters
+ * that are properly escaped by backslash.
+ */
+struct StringSplitter<'a> {
+	chars: Chars<'a>
+}
+
+impl Iterator for StringSplitter<'_> {
+	type Item = String;
+	
+	fn next(&mut self) -> Option<String> {
+		let mut next_char = self.chars.next();
+		
+		if next_char == None {
+			return None;
+		}
+		
+		let mut escaped = false;
+		let mut collector = String::new();
+		
+		loop {
+			match next_char {
+				Some('\\') if !escaped => {
+					escaped = true;
+				},
+				Some('|') if !escaped => {
+					return Some(collector);
+				},
+				Some(c) => {
+					escaped = false;
+					collector.push(c);
+				},
+				None => return Some(collector)
+			}
+			
+			next_char = self.chars.next();
+		}
+	}
+}
+
+fn split_with_escaped_delimeter(s: &str) -> StringSplitter {
+	StringSplitter{chars: s.chars()}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use chrono::{Datelike, Timelike};
+	
+	#[test]
+	fn start() {
+		let t = Activity::start(project::Project("test project".to_string()), "test description".to_string());		
+		assert_eq!(t.description, "test description".to_string());
+		assert_eq!(t.project.0, "test project".to_string());
+		assert_eq!(t.end, None);
+	}
+
+	#[test]
+	fn stop() {
+		let mut t = Activity::start(project::Project("test project".to_string()), "test description".to_string());		
+		t.stop();		
+		assert_ne!(t.end, None);
+	}
+
+
+	#[test]
+	fn display() {
+		let mut t = Activity::start(project::Project("test project| 1".to_string()), "test\\description".to_string());		
+		t.start = NaiveDateTime::parse_from_str("2021-02-16 16:14", conf::FORMAT_DATETIME).unwrap();		
+		assert_eq!(format!("{}", t), "2021-02-16 16:14 | test project\\| 1 | test\\\\description\n");		
+		t.end = Some(NaiveDateTime::parse_from_str("2021-02-16 18:23" , conf::FORMAT_DATETIME).unwrap());		
+		assert_eq!(format!("{}", t), "2021-02-16 16:14 - 2021-02-16 18:23 | test project\\| 1 | test\\\\description\n");
+	}
+	
+	#[test]
+	fn from_str_running_activity() {
+		let t = Activity::from_str("2021-02-16 16:14 | test project | test description").unwrap();
+		
+		assert_eq!(t.start.date().year(), 2021);
+		assert_eq!(t.start.date().month(), 2);
+		assert_eq!(t.start.date().day(), 16);
+		
+		assert_eq!(t.start.time().hour(), 16);
+		assert_eq!(t.start.time().minute(), 14);
+		
+		assert_eq!(t.description, "test description".to_string());
+		assert_eq!(t.project.0, "test project".to_string());
+		assert_eq!(t.end, None);		
+	}
+	
+	#[test]
+	fn from_str_running_activity_no_description() {
+		let t = Activity::from_str("2021-02-16 16:14 | test project").unwrap();
+		
+		assert_eq!(t.start.date().year(), 2021);
+		assert_eq!(t.start.date().month(), 2);
+		assert_eq!(t.start.date().day(), 16);
+		
+		assert_eq!(t.start.time().hour(), 16);
+		assert_eq!(t.start.time().minute(), 14);
+		
+		assert_eq!(t.description, "".to_string());
+		assert_eq!(t.project.0, "test project".to_string());
+		assert_eq!(t.end, None);		
+	}
+	
+	#[test]
+	fn from_str_stopped_activity() {
+		let t = Activity::from_str("2021-02-16 16:14 - 2021-02-16 18:23 | test project | test description").unwrap();
+		
+		assert_ne!(t.end, None);
+		
+		let end = t.end.unwrap();
+		
+		assert_eq!(end.date().year(), 2021);
+		assert_eq!(end.date().month(), 2);
+		assert_eq!(end.date().day(), 16);
+		
+		assert_eq!(end.time().hour(), 18);
+		assert_eq!(end.time().minute(), 23);
+
+	}
+
+	#[test]
+	fn from_str_escaped_chars() {
+		let t = Activity::from_str("2021-02-16 16:14 - 2021-02-16 18:23 | test project\\| 1 | test\\\\description").unwrap();
+		
+		assert_eq!(t.project.0, "test project| 1");
+		assert_eq!(t.description, "test\\description");
+	}
+	
+	#[test]
+	fn string_roundtrip() {
+		let mut t = Activity::start(project::Project("ex\\ample\\\\pro|ject".to_string()), "e\\\\xam|||ple tas\t\t\nk".to_string());
+		t.stop();
+		let t2 = Activity::from_str(format!("{}", t).as_str()).unwrap();
+		
+		assert_eq!(t.start.with_second(0).unwrap().with_nanosecond(0).unwrap(), t2.start);
+		assert_eq!(t.end.unwrap().with_second(0).unwrap().with_nanosecond(0).unwrap(), t2.end.unwrap());
+		
+		assert_eq!(t.project.0, t2.project.0);
+		assert_eq!(t.description, t2.description);
+	}
+	
+	#[test]
+	fn from_str_errors() {
+		let t = Activity::from_str("2021 test project");
+		assert!(matches!(t, Err(ActivityError::GeneralParseError)));
+		
+		let t = Activity::from_str("asb - 2021- | project");
+		assert!(matches!(t, Err(ActivityError::DateTimeParseError)));
+	}
+}
\ No newline at end of file