diff --git a/sources/VYLET.cpp b/sources/VYLET.cpp
index e0a421e..f66f955 100644
--- a/sources/VYLET.cpp
+++ b/sources/VYLET.cpp
@@ -258,7 +258,7 @@ VYLETData::Data VYLETData::ReadL() const
   {
    time        = R2Time((*vylet)[tcol - 1][iy * lons.size() + ix]);
    lambda      = (*vylet)[lcol - 1][iy * lons.size() + ix];
-   days        = (time - start).D();
+   days        = (invtime ? -1.0 : 1.0) * (time - start).D();
    out(ix, iy) = lambda / days;
   }
 
@@ -297,7 +297,7 @@ VYLETData::Data VYLETData::ReadT() const
    x    = (*vylet)[2][iy * lons.size() + ix];
    y    = (*vylet)[3][iy * lons.size() + ix];
    time = R2Time((*vylet)[tcol - 1][iy * lons.size() + ix]);
-   days = (time - start).D();
+   days = (invtime ? -1.0 : 1.0) * (time - start).D();
    if(days <= tstep * 1.5) days = 0.0;
    inside  = x > xl && x < xr && y > yd && y < yu;
    maxtime = days >= maxdays - tstep * 0.5;
@@ -515,7 +515,7 @@ VYLETData::Data VYLETData::ReadTmask() const
   for(size_t ix = 0; ix < lons.size(); ix++)
   {
    time        = R2Time((*vylet)[tcol - 1][iy * lons.size() + ix]);
-   days        = (time - start).D();
+   days        = (invtime ? -1.0 : 1.0) * (time - start).D();
    maxtime     = days >= maxdays - tstep * 0.5;
    out(ix, iy) = maxtime ? 1.0 : NAN;
   }