diff --git a/cxx/mcc_mount_pz.h b/cxx/mcc_mount_pz.h
index 4fc29fa..8a1dd55 100644
--- a/cxx/mcc_mount_pz.h
+++ b/cxx/mcc_mount_pz.h
@@ -16,7 +16,7 @@
 namespace mcc
 {
 
-static constexpr double mcc_UT1_to_sideral_ratio = 1.002737909350795;  // UT1/sideral
+static constexpr double mcc_sideral_to_UT1_ratio = 1.002737909350795;  // sideral/UT1
 
 /*  SOME SIMPLE PROHIBITED ZONE IMPLEMENTATIONS  */
 
@@ -86,7 +86,13 @@ public:
             return infDuration;
         }
 
-        return compute(telemetry_data);
+        if constexpr (KIND ==
+                      MccAltLimitKind::MIN_ALT_LIMIT) {  // the closest time point is one after upper culmination
+            return compute(telemetry_data, false);
+        } else if constexpr (KIND == MccAltLimitKind::MAX_ALT_LIMIT) {  // the closest time point is one before upper
+                                                                        // culmination
+            return compute(telemetry_data, true);
+        }
     }
 
     // returns a time to exit from the zone
@@ -100,7 +106,13 @@ public:
             return zeroDuration;
         }
 
-        return compute(telemetry_data);
+        if constexpr (KIND ==
+                      MccAltLimitKind::MIN_ALT_LIMIT) {  // the closest time point is one before upper culmination
+            return compute(telemetry_data, true);
+        } else if constexpr (KIND == MccAltLimitKind::MAX_ALT_LIMIT) {  // the closest time point is one after upper
+                                                                        // culmination
+            return compute(telemetry_data, false);
+        }
     }
 
     template <std::derived_from<MccAngle> XT, std::derived_from<MccAngle> YT>
@@ -174,7 +186,7 @@ private:
         return true;
     }
 
-    pz_duration_t compute(traits::mcc_mount_telemetry_data_c auto const& telemetry_data)
+    pz_duration_t compute(traits::mcc_mount_telemetry_data_c auto const& telemetry_data, bool before_upper_culm)
     {
         double cos_ha = (std::sin(_altLimit) - std::sin(telemetry_data.mntDEC) * std::sin(_latitude)) /
                         std::cos(telemetry_data.mntDEC) / std::cos(_latitude);
@@ -183,12 +195,31 @@ private:
             return infDuration;
         }
 
-        MccAngle time_ang = std::acos(cos_ha) - telemetry_data.mntHA;  // in sideral time scale
-        if (time_ang < 0.0) {                                          // next day
+        double ha;
+        if (before_upper_culm) {
+            ha = -std::acos(cos_ha);  // HA before upper culmination
+        } else {
+            ha = std::acos(cos_ha);  // HA after upper culmination!!
+        }
+
+        // if constexpr (KIND == MccAltLimitKind::MIN_ALT_LIMIT) {  // the closest time moment after upper
+        // culmination!!!
+        //     ha = std::acos(cos_ha);                              // HA after upper culmination!!
+        // } else if constexpr (KIND ==
+        //                      MccAltLimitKind::MAX_ALT_LIMIT) {  // the closest time moment before upper
+        //                      culmination!!!
+        //     ha = -std::acos(cos_ha);                            // HA before upper culmination
+        // } else {
+        //     static_assert(false, "UNKNOWN ALTITUDE LIMIT TYPE!");
+        // }
+
+        MccAngle time_ang = ha - telemetry_data.mntHA;  // in sideral time scale
+
+        if (time_ang < 0.0) {  // next day
             time_ang += pi2;
         }
 
-        time_ang *= mcc_UT1_to_sideral_ratio;
+        time_ang /= mcc_sideral_to_UT1_ratio;  // to UT1 time scale
 
         return pz_duration_t{time_ang.seconds()};
     }
diff --git a/cxx/tests/astrom_test.cpp b/cxx/tests/astrom_test.cpp
index 67e9984..0a93c88 100644
--- a/cxx/tests/astrom_test.cpp
+++ b/cxx/tests/astrom_test.cpp
@@ -219,6 +219,14 @@ int main(int argc, char* argv[])
         std::cout << "(MINALT) time to zone: " << std::chrono::hh_mm_ss(tm) << " (" << now1 << ")\n";
     }
 
+    tm = minalt_pz.timeFrom(tdata);
+    if (std::isinf(tm.count())) {
+        std::cout << "(MINALT) time from zone: the object never reaches the zone!\n";
+    } else {
+        auto now1 = now + std::chrono::duration_cast<decltype(now)::duration>(tm);
+        std::cout << "(MINALT) time from zone: " << std::chrono::hh_mm_ss(tm) << " (" << now1 << ")\n";
+    }
+
     std::cout << "\n";
 
     ra1 = "17:00:00"_hms;
@@ -235,13 +243,27 @@ int main(int argc, char* argv[])
 
     tdata = {ra_o, dec_o, ha1, az1, alt1, 0.0, 0.0};
 
+    jd.mjd += 1.0;
+    res = erfa.icrs2obs(ra1, dec1, jd, ra_o, dec_o, ha1, az1, alt1, eor);
+    std::cout << "RA_app (+24h) = " << ra_o.sexagesimal(true) << "\n";
+
     tm = maxalt_pz.timeTo(tdata);
     if (std::isinf(tm.count())) {
         std::cout << "(MAXALT) time to zone: the object never reaches the zone!\n";
     } else {
+        // auto ns = std::chrono::duration_cast<std::chrono::nanoseconds>(tm);
         auto now1 = now + std::chrono::duration_cast<decltype(now)::duration>(tm);
+        // auto now1 = now + ns;
         std::cout << "(MAXALT) time to zone: " << std::chrono::hh_mm_ss(tm) << " (" << now1 << ")\n";
     }
 
+    tm = maxalt_pz.timeFrom(tdata);
+    if (std::isinf(tm.count())) {
+        std::cout << "(MAXALT) time from zone: the object never reaches the zone!\n";
+    } else {
+        auto now1 = now + std::chrono::duration_cast<decltype(now)::duration>(tm);
+        std::cout << "(MAXALT) time from zone: " << std::chrono::hh_mm_ss(tm) << " (" << now1 << ")\n";
+    }
+
     return ecode;
 }