diff --git a/Overlap/Tests/test_overlap.f90 b/Overlap/Tests/test_overlap.f90
index da6fb18d5f0bdcbb1507c8e794f717b5aaa6525d..6febf24a70eeb980308741ab782c523035822d51 100644
--- a/Overlap/Tests/test_overlap.f90
+++ b/Overlap/Tests/test_overlap.f90
@@ -103,7 +103,7 @@ program test_overlap
 
   call shpc_create(hshp, shpc_dir = "SHPC", cyclone = hshp%cyclone)
   call init_interpolated_eddy
-  call overlap(flow, nlon, nlat, periodic, dist_lim, hshp, k = k_test_2, &
+  call overlap(flow, nlon, nlat, periodic, dist_lim, hshp, d = k_test_2, &
        delta = max_delta, j = max_delta + 1)
   close(unit_edge)
   print *, 'Created file "edgelist.csv".'
diff --git a/Overlap/overlap.f90 b/Overlap/overlap.f90
index da2433e5f2393db0ae1dc3d52e96144cc0423e02..267f10351cd64c2d469585755e367d13df98c096 100644
--- a/Overlap/overlap.f90
+++ b/Overlap/overlap.f90
@@ -4,11 +4,11 @@ module overlap_m
 
 contains
 
-  subroutine overlap(flow, nlon, nlat, periodic, dist_lim, hshp_interp, k, &
+  subroutine overlap(flow, nlon, nlat, periodic, dist_lim, hshp_interp, d, &
        delta, j)
 
     ! This procedure finds edges between flow(j - delta) and flow(j),
-    ! corresponding to dates k - delta and k. It calls write_overlap
+    ! corresponding to dates d - delta and d. It calls write_overlap
     ! for these edges. It updates flow(j - delta)%list_vis%delta_out,
     ! flow(j)%list_vis%delta_in and flow(j - delta + 1:j -
     ! 1)%number_eddies.
@@ -36,7 +36,7 @@ contains
     ! Collection of shapefiles to which any interpolated eddy will be written:
     TYPE(shpc), intent(in):: hshp_interp
 
-    integer, intent(in):: k ! date index
+    integer, intent(in):: d ! date, in days since 1950-1-1
     integer, intent(in):: delta ! between 1 and max_delta
 
     integer, intent(in):: j
@@ -122,7 +122,7 @@ contains
                    flow(j - delta + 1:j - 1)%number_eddies &
                         = flow(j - delta + 1:j - 1)%number_eddies + 1
 
-                   call write_overlap(hshp_interp, k, delta, i1, i2, m, &
+                   call write_overlap(hshp_interp, d, delta, i1, i2, m, &
                         flow(j - delta + 1:j - 1)%number_eddies, &
                         flow(j - delta)%list_vis(i1)%cyclone, &
                         flow(j - delta)%list_vis(i1)%coord_extr, &