diff --git a/apps/api/src/reservations/reservations.service.ts b/apps/api/src/reservations/reservations.service.ts
index 2aef008..20c405a 100644
--- a/apps/api/src/reservations/reservations.service.ts
+++ b/apps/api/src/reservations/reservations.service.ts
@@ -31,6 +31,17 @@ export class ReservationsService {
       throw new BadRequestException('Start time must be before end time');
     }
 
+    const now = new Date();
+    if (space.type === SpaceType.DESK) {
+      const today = new Date();
+      today.setHours(0, 0, 0, 0);
+      if (start < today) {
+        throw new BadRequestException('Cannot book desks in the past');
+      }
+    } else if (start < now) {
+      throw new BadRequestException('Cannot book in the past');
+    }
+
     // Rules
     if (space.type === SpaceType.DESK) {
       // Desks: Full day (setting to midnight of start and end of that day)
@@ -204,6 +215,17 @@ export class ReservationsService {
       throw new BadRequestException('Start time must be before end time');
     }
 
+    const now = new Date();
+    if (space.type === SpaceType.DESK) {
+      const today = new Date();
+      today.setHours(0, 0, 0, 0);
+      if (start < today) {
+        throw new BadRequestException('Cannot update desk reservation to the past');
+      }
+    } else if (start < now) {
+      throw new BadRequestException('Cannot update reservation to the past');
+    }
+
     // Rules
     if (space.type === SpaceType.DESK) {
       start.setHours(0, 0, 0, 0);
diff --git a/apps/web/src/lib/components/BookingModal.svelte b/apps/web/src/lib/components/BookingModal.svelte
index d3fae87..d8ce122 100644
--- a/apps/web/src/lib/components/BookingModal.svelte
+++ b/apps/web/src/lib/components/BookingModal.svelte
@@ -72,6 +72,14 @@
         start.setHours(0, 0, 0, 0);
         end = new Date(bookingDate);
         end.setHours(23, 59, 59, 999);
+
+        const today = new Date();
+        today.setHours(0, 0, 0, 0);
+        if (start < today) {
+          error = $t('booking.errorPast');
+          loading = false;
+          return;
+        }
       } else {
         const [sh, sm] = startTime.split(':').map(Number);
         const [eh, em] = endTime.split(':').map(Number);
@@ -82,6 +90,12 @@
         end = new Date(bookingDate);
         end.setHours(eh, em, 0, 0);
 
+        if (start < new Date()) {
+          error = $t('booking.errorPast');
+          loading = false;
+          return;
+        }
+
         if (end <= start) {
           error = $t('booking.errorTime');
           loading = false;
@@ -143,6 +157,10 @@
     const slotStart = new Date(bookingDate);
     slotStart.setHours(h, m, 0, 0);
     
+    if (slotStart < new Date()) {
+      return { isPast: true };
+    }
+
     return dayReservations.find(r => {
       const rStart = new Date(r.startTime);
       const rEnd = new Date(r.endTime);
@@ -287,12 +305,13 @@
                       <button 
                         type="button"
                         on:click={() => selectSlot(time)}
-                        disabled={!!reservation && reservation.userId !== $user?.id && reservation.user?.id !== $user?.id && $user?.role !== 'ADMIN'}
+                        disabled={(!!reservation && reservation.userId !== $user?.id && reservation.user?.id !== $user?.id && $user?.role !== 'ADMIN') || (reservation && reservation.isPast)}
                         class="w-full py-2 text-[10px] font-bold rounded-md transition-all border
-                          {reservation ? 'bg-red-100 text-red-700 border-red-200' : 
+                          {reservation?.isPast ? 'bg-gray-100 text-gray-400 border-gray-200 cursor-not-allowed' : 
+                           reservation ? 'bg-red-100 text-red-700 border-red-200' : 
                            startTime === time ? 'bg-indigo-600 text-white border-indigo-700 ring-2 ring-indigo-200' : 
                            'bg-white text-gray-600 border-gray-200 hover:border-indigo-400'}"
-                        title={reservation ? $t('booking.bookedBy', { values: { user: reservation.user.email } }) : $t('booking.availableAt', { values: { time: time } })}
+                        title={reservation?.isPast ? $t('booking.past') : reservation ? $t('booking.bookedBy', { values: { user: reservation.user.email } }) : $t('booking.availableAt', { values: { time: time } })}
                       >
                         {time}
                       </button>
diff --git a/apps/web/src/lib/i18n/locales/en.json b/apps/web/src/lib/i18n/locales/en.json
index 20dd97c..c34fadd 100644
--- a/apps/web/src/lib/i18n/locales/en.json
+++ b/apps/web/src/lib/i18n/locales/en.json
@@ -77,6 +77,8 @@
     "errorCreating": "Failed to create booking",
     "errorDeleting": "Failed to delete booking",
     "errorTime": "End time must be after start time",
+    "errorPast": "Cannot book in the past",
+    "past": "This time has already passed",
     "spaceType": {
       "DESK": "Desk",
       "MEETING_ROOM": "Meeting Room",
diff --git a/apps/web/src/lib/i18n/locales/es-ES.json b/apps/web/src/lib/i18n/locales/es-ES.json
index cc08f65..0c7947f 100644
--- a/apps/web/src/lib/i18n/locales/es-ES.json
+++ b/apps/web/src/lib/i18n/locales/es-ES.json
@@ -77,6 +77,8 @@
     "errorCreating": "Error al crear la reserva",
     "errorDeleting": "Error al eliminar la reserva",
     "errorTime": "La hora de finalización debe ser posterior a la de inicio",
+    "errorPast": "No se puede reservar en el pasado",
+    "past": "Esta hora ya ha pasado",
     "spaceType": {
       "DESK": "Puesto",
       "MEETING_ROOM": "Sala de reuniones",
diff --git a/apps/web/src/routes/dashboard/building/[id]/+page.svelte b/apps/web/src/routes/dashboard/building/[id]/+page.svelte
index dededd5..b22ecef 100644
--- a/apps/web/src/routes/dashboard/building/[id]/+page.svelte
+++ b/apps/web/src/routes/dashboard/building/[id]/+page.svelte
@@ -108,6 +108,7 @@
             id="date-select"
             type="date"
             bind:value={selectedDateString}
+            min={new Date().toISOString().split('T')[0]}
             class="absolute inset-0 opacity-0 cursor-pointer z-10 w-full h-full"
             on:click={(e) => e.currentTarget.showPicker()}
           />
diff --git a/apps/web/src/routes/dashboard/floor/[id]/+page.svelte b/apps/web/src/routes/dashboard/floor/[id]/+page.svelte
index e559c20..82fc302 100644
--- a/apps/web/src/routes/dashboard/floor/[id]/+page.svelte
+++ b/apps/web/src/routes/dashboard/floor/[id]/+page.svelte
@@ -69,6 +69,7 @@
             id="date-select"
             type="date"
             bind:value={selectedDateString}
+            min={new Date().toLocaleDateString('en-CA')}
             class="absolute inset-0 opacity-0 cursor-pointer z-10 w-full h-full"
             on:click={(e) => e.currentTarget.showPicker()}
           />
diff --git a/apps/web/src/routes/dashboard/my-bookings/+page.svelte b/apps/web/src/routes/dashboard/my-bookings/+page.svelte
index 163b83f..ce7ef2b 100644
--- a/apps/web/src/routes/dashboard/my-bookings/+page.svelte
+++ b/apps/web/src/routes/dashboard/my-bookings/+page.svelte
@@ -74,6 +74,21 @@
       const start = new Date(`${editStartTimeDate}T${editStartTimeTime}`);
       const end = new Date(`${editEndTimeDate}T${editEndTimeTime}`);
       
+      const now = new Date();
+      if (editingReservation.space.type === 'DESK') {
+        const today = new Date();
+        today.setHours(0, 0, 0, 0);
+        if (start < today) {
+          alert($t('booking.errorPast'));
+          saving = false;
+          return;
+        }
+      } else if (start < now) {
+        alert($t('booking.errorPast'));
+        saving = false;
+        return;
+      }
+
       await apiFetch(`/reservations/${editingReservation.id}`, {
         method: "PATCH",
         body: JSON.stringify({
@@ -268,6 +283,7 @@
                <input 
                  type="date" 
                  bind:value={editStartTimeDate}
+                 min={new Date().toISOString().split('T')[0]}
                  class="absolute inset-0 opacity-0 cursor-pointer w-full z-10"
                  on:click={(e) => e.currentTarget.showPicker()}
                />