diff --git a/src/commands/display.rs b/src/commands/display.rs
index e37175b..0ebf2a4 100644
--- a/src/commands/display.rs
+++ b/src/commands/display.rs
@@ -74,6 +74,7 @@ where
     format.print_formatted(
         entries,
         &mut streams.out,
+        &mut streams.err,
         facts,
         ids,
     )?;
diff --git a/src/error.rs b/src/error.rs
index b8d23ae..81c1463 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -4,6 +4,15 @@ use std::io;
 
 use thiserror::Error;
 use chrono::NaiveDateTime;
+use itertools::Itertools;
+
+fn format_paths(paths: &[PathBuf]) -> String {
+    paths
+        .iter()
+        .map(|p| format!("    - {}", p.display()))
+        .collect_vec()
+        .join("\n")
+}
 
 #[derive(Debug, Error)]
 pub enum Error {
@@ -11,9 +20,9 @@ pub enum Error {
     UnimplementedCommand(String),
 
     /// Sometimes a specific variant for an error is not necessary if the error
-    /// can only happen in one place in the code. This is that the generic error
+    /// can only happen in one place in the code. This is what the generic error
     /// is for and nothing else.
-    #[error("Error: {0}")]
+    #[error("{0}")]
     GenericFailure(String),
 
     #[error("Sqlite error: {0}")]
@@ -180,6 +189,42 @@ Is there a permissions issue? Here's the underlaying error:
 
     #[error("Trying to run system command sqlite3 failed")]
     Sqlite3CommandFailedUnkown,
+
+    #[error("The specified name for a custom formatter \"{0}\" is not valid. Only ascii
+letters, numbers, dots, dashes and underscores are allowed.")]
+    InvalidCustomFormatter(String),
+
+    #[error("You have specified a custom formatter \"{0}\" but your config file doesn't say
+where to look for it.
+
+You can set a path using
+
+t config --formatter-search-paths <path>..")]
+    NoFormatterSearchPaths(String),
+
+    #[error("Could not find a formatter with name '{name}' in any of the following paths:
+
+{0}
+
+which where taken from your config file located at
+
+    {config_at}
+
+Perhaps is mispelled?", format_paths(.paths))]
+    FormatterNotFound {
+        name: String,
+        paths: Vec<PathBuf>,
+        config_at: PathBuf,
+    },
+
+    #[error("The custom formatter located at:
+
+{0}
+
+failed with error:
+
+{1}")]
+    CustomFormatterFailed(PathBuf, std::io::Error),
 }
 
 pub type Result<T> = result::Result<T, Error>;
diff --git a/src/formatters.rs b/src/formatters.rs
index b1a8064..785eb61 100644
--- a/src/formatters.rs
+++ b/src/formatters.rs
@@ -12,6 +12,7 @@ pub mod csv;
 pub mod json;
 pub mod ids;
 pub mod ical;
+pub mod custom;
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename_all = "lowercase")]
@@ -37,16 +38,18 @@ impl Formatter {
     /// to the local timezone is given in `offset` to prevent this function from
     /// using a secondary effect to retrieve the time and conver dates. This
     /// also makes it easier to test.
-    pub fn print_formatted<W: Write>(&self, entries: Vec<Entry>, out: &mut W, facts: &Facts, ids: bool) -> error::Result<()> {
+    pub fn print_formatted<O, E>(&self, entries: Vec<Entry>, out: &mut O, err: &mut E, facts: &Facts, ids: bool) -> error::Result<()>
+    where
+        O: Write,
+        E: Write,
+    {
         match &self {
             Formatter::Text => text::print_formatted(entries, out, facts, ids)?,
             Formatter::Csv => csv::print_formatted(entries, out, ids)?,
             Formatter::Json => json::print_formatted(entries, out)?,
             Formatter::Ids => ids::print_formatted(entries, out)?,
             Formatter::Ical => ical::print_formatted(entries, out, facts.now)?,
-            Formatter::Custom(name) => {
-                panic!("attempted custom formatter with name {} which is not implemented", name);
-            }
+            Formatter::Custom(name) => custom::print_formatted(name, entries, out, err, facts)?,
         }
 
         Ok(())
diff --git a/src/formatters/custom.rs b/src/formatters/custom.rs
new file mode 100644
index 0000000..84c17e3
--- /dev/null
+++ b/src/formatters/custom.rs
@@ -0,0 +1,158 @@
+use std::io::Write;
+use std::path::PathBuf;
+use std::process::{Command, Stdio};
+use std::io::Read;
+
+use csv::Writer;
+use chrono::SecondsFormat;
+
+use crate::error::{Result, Error::*};
+use crate::models::Entry;
+use crate::commands::Facts;
+
+/// tries to find a formatter with the given name in one of the possible paths
+fn formatter_path(formatters: &[PathBuf], name: &str) -> Option<PathBuf> {
+    formatters.iter().find_map(|f| {
+        let mut path = f.clone();
+
+        path.push(name);
+
+        if path.exists() {
+            Some(path)
+        } else {
+            None
+        }
+    })
+}
+
+fn is_valid_formatter_name(formatter: &str) -> bool {
+    formatter.chars().filter(|&c| {
+        !(c.is_alphanumeric() || c == '.' || c == '-' || c == '_')
+    }).count() == 0
+}
+
+pub fn print_formatted<O, E>(formatter: &str, entries: Vec<Entry>, out: &mut O, err: &mut E, facts: &Facts) -> Result<()>
+where
+    O: Write,
+    E: Write,
+{
+    if !is_valid_formatter_name(formatter) {
+        return Err(InvalidCustomFormatter(formatter.into()));
+    }
+
+    if facts.config.formatter_search_paths.is_empty() {
+        return Err(NoFormatterSearchPaths(formatter.into()));
+    }
+
+    let path = formatter_path(&facts.config.formatter_search_paths, formatter).ok_or_else(|| FormatterNotFound {
+        name: formatter.into(),
+        paths: facts.config.formatter_search_paths.clone(),
+        config_at: facts.config.path.clone().unwrap_or_else(|| "in memory".into()),
+    })?;
+
+    let config = "{}";
+
+    let mut command = Command::new(&path);
+
+    command
+        .arg(config)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped());
+
+    let mut child = command.spawn().map_err(|e| CustomFormatterFailed(path, e))?;
+
+    let stdin = child.stdin.take().expect("Failed to take stdin");
+    let mut stdout = child.stdout.take().expect("Failed to take stdout");
+    let mut stderr = child.stderr.take().expect("Failed to take stdout");
+
+    let mut wtr = Writer::from_writer(stdin);
+    let mut captured_out = Vec::new();
+    let mut captured_err = Vec::new();
+
+    for entry in entries {
+        // write to process' stdin
+        wtr.write_record(&[
+            entry.id.to_string(),
+            entry.start.to_rfc3339_opts(SecondsFormat::Micros, true),
+            entry.end.map(|t| t.to_rfc3339_opts(SecondsFormat::Micros, true)).unwrap_or_else(|| "".into()),
+            entry.note.unwrap_or_else(|| "".into()),
+            entry.sheet,
+        ])?;
+
+        // read process' stdout and stderr
+        stdout.read_to_end(&mut captured_out)?;
+        write!(out, "{}", String::from_utf8_lossy(&captured_out))?;
+        captured_out.clear();
+
+        stderr.read_to_end(&mut captured_err)?;
+        write!(err, "{}", String::from_utf8_lossy(&captured_err))?;
+        captured_err.clear();
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::config::Config;
+
+    use super::*;
+
+    #[test]
+    fn errors_if_invalid_formatter_name() {
+        let mut out = Vec::new();
+        let mut err = Vec::new();
+        let facts = Facts::new();
+        let err = print_formatted("pol/lo", Vec::new(), &mut out, &mut err, &facts).unwrap_err();
+
+        assert_eq!(err.to_string(), "\
+The specified name for a custom formatter \"pol/lo\" is not valid. Only ascii
+letters, numbers, dots, dashes and underscores are allowed.
+");
+    }
+
+    #[test]
+    fn errors_if_no_formatter_search_paths() {
+        let mut out = Vec::new();
+        let mut err = Vec::new();
+        let facts = Facts::new();
+        let err = print_formatted("pollo", Vec::new(), &mut out, &mut err, &facts).unwrap_err();
+
+        assert_eq!(err.to_string(), "\
+You have specified a custom formatter \"pollo\" but your config file doesn't say
+where to look for it.
+
+You can set a path using
+
+t config --formatter-search-paths <path>..
+");
+    }
+
+    #[test]
+    fn nice_error_if_no_such_formatter() {
+        let mut out = Vec::new();
+        let mut err = Vec::new();
+        let facts = Facts::new().with_config(Config {
+            formatter_search_paths: vec![
+                PathBuf::from("/not/a/path"),
+                PathBuf::from("/tmp/foo/var"),
+            ],
+            path: Some(PathBuf::from("/etc/tiempo/config.toml")),
+            ..Default::default()
+        });
+        let err = print_formatted("pollo", Vec::new(), &mut out, &mut err, &facts).unwrap_err();
+
+        assert_eq!(err.to_string(), "\
+Could not find a formatter with name 'pollo' in any of the following paths:
+
+    - /not/a/path
+    - /tmp/foo/var
+
+which where taken from your config file located at
+
+    /etc/tiempo/config.toml
+
+Perhaps is mispelled?");
+    }
+}