diff --git a/pyproject.toml b/pyproject.toml
index d340ded..ecce15f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,6 +35,7 @@ dependencies = [
     "requests",
     "xarray",
     "cdsapi >= 0.7.2",
+    "cftime",
 ]
 dynamic = [
     "version",
diff --git a/requirements.txt b/requirements.txt
index 89548d7..b05bc21 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,6 @@
 bmipy
 cdsapi>=0.7.2
+cftime
 netcdf4
 numpy
 pyyaml