diff --git a/src/main.rs b/src/main.rs
index 7711973..ca3daa6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -191,6 +191,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: encounters,
                     joins: vec![],
+                    date_order_column: Some("StartDateTime".to_owned()),
                 },
             );
             inputs.insert(
@@ -198,6 +199,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: services,
                     joins: vec![],
+                    date_order_column: Some("StartDateTime".to_owned()),
                 },
             );
             inputs.insert(
@@ -205,6 +207,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: transfers,
                     joins: vec![],
+                    date_order_column: Some("StartDateTime".to_owned()),
                 },
             );
             inputs.insert(
@@ -212,6 +215,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: procedures,
                     joins: vec![],
+                    date_order_column: Some("ProcedureDateTime".to_owned()),
                 },
             );
             inputs.insert(
@@ -219,6 +223,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: diagnoses,
                     joins: vec![],
+                    date_order_column: None,
                 },
             );
             inputs.insert(
@@ -226,6 +231,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: patients,
                     joins: vec![],
+                    date_order_column: None,
                 },
             );
             inputs.insert(
@@ -233,6 +239,7 @@ fn main() -> anyhow::Result<()> {
                 InputFile {
                     file_path: revenues,
                     joins: vec![],
+                    date_order_column: None,
                 },
             );
             coster_rs::create_products::create_products_polars(definitions, inputs, output)
diff --git a/src/products/create_products.rs b/src/products/create_products.rs
index 95d3f36..337e236 100644
--- a/src/products/create_products.rs
+++ b/src/products/create_products.rs
@@ -37,6 +37,8 @@ struct Product {
 pub struct InputFile {
     pub file_path: PathBuf,
     pub joins: Vec<FileJoin>,
+    // if not specified, then don't allow change in type builds, as there's no way to detect changes over time
+    pub date_order_column: Option<String>,
 }
 
 pub fn create_products_polars(
@@ -49,7 +51,6 @@ pub fn create_products_polars(
     for definition in definitions {
         build_polars(definition, &inputs, &output_path)?;
     }
-
     Ok(())
 }