diff --git a/cmd/dayOff.go b/cmd/dayOff.go
new file mode 100644
index 0000000..262666e
--- /dev/null
+++ b/cmd/dayOff.go
@@ -0,0 +1,61 @@
+package cmd
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+const dFormat = "2006-01-02"
+
+// dayOffCmd represents the dayOff command
+var dayOffCmd = &cobra.Command{
+	Use:   "dayOff [day]",
+	Short: "Add a day that isn't calcualted for total. (format: 2016-04-28)",
+	Args: func(cmd *cobra.Command, args []string) error {
+		if len(args) != 1 {
+			return errors.New("requires a day (format: 2016-04-28)")
+		}
+		if validDay(args[0]) {
+			return nil
+		}
+		return fmt.Errorf("invalid day format (yyyy-mm-dd): %s", args[0])
+	},
+	Run: func(cmd *cobra.Command, args []string) {
+		addDayOff(args[0])
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(dayOffCmd)
+}
+
+func validDay(day string) bool {
+	_, err := time.Parse(dFormat, day)
+	if err != nil {
+		return false
+	}
+	return true
+}
+
+func addDayOff(day string) {
+	t, _ := time.Parse(dFormat, day)
+	newDay := t.Format(dFormat)
+	days := viper.GetStringSlice("days_off")
+	for _, d := range days {
+		if d == newDay {
+			fmt.Println(newDay, "already exists")
+			return
+		}
+	}
+	days = append(days, newDay)
+
+	viper.Set("days_off", days)
+	if err := viper.WriteConfig(); err != nil {
+		fmt.Println("problem with updating config file", err)
+	}
+	return
+}
diff --git a/cmd/report.go b/cmd/report.go
index 0e7c605..cfde8a9 100644
--- a/cmd/report.go
+++ b/cmd/report.go
@@ -39,9 +39,11 @@ func runReport(format string) {
 		panic(err)
 	}
 	filename := viper.GetString("tracking_file")
+	daysOff := viper.GetStringSlice("days_off")
 
 	fmt.Printf("hours worked this week: %.1f \n", reporting.HoursWorkedThisWeek(filename, user.Username))
-	fmt.Printf("hours worked this month: %.1f \n", reporting.HoursWorkedThisMonth(filename, user.Username))
+	fmt.Printf("hours worked this month: %.1f \n", reporting.HoursWorkedThisMonth(filename, user.Username, daysOff))
+	fmt.Printf("   out of possible days: %d \n", reporting.AvailableDaysThisMonth(time.Now(), daysOff))
 	fmt.Println("-------------")
 
 	fmt.Println(reporting.TextCalendar(time.Now(), filename, user.Username))
diff --git a/pkg/reporting/simple.go b/pkg/reporting/simple.go
index 20a42cb..b355342 100644
--- a/pkg/reporting/simple.go
+++ b/pkg/reporting/simple.go
@@ -1,6 +1,7 @@
 package reporting
 
 import (
+	"fmt"
 	"strconv"
 	"time"
 )
@@ -32,22 +33,56 @@ func sumThisWeek(data Years, t time.Time) float64 {
 }
 
 // HoursWorkedThisMonth returns the total hours documented per day for the current month
-func HoursWorkedThisMonth(filename, user string) float64 {
+func HoursWorkedThisMonth(filename, user string, daysOff []string) float64 {
 	data := getTrackedData(filename)[user]
 	now := time.Now()
 
-	return sumThisMonth(data, now)
+	return sumThisMonth(data, now, daysOff)
 }
 
-func sumThisMonth(data Years, t time.Time) float64 {
+func sumThisMonth(data Years, t time.Time, daysOff []string) float64 {
 	thisDay := t
 	y := strconv.Itoa(thisDay.Year())
 	m := thisDay.Month().String() // uses month name - might "break" if user switches locales
 	days := data[y][m]
 
 	sum := 0
-	for _, d := range days {
-		sum += d
+	for key, d := range days {
+		day, _ := strconv.Atoi(key)
+		if !isDayOff(daysOff, fmt.Sprintf("%s-%02d-%02d", y, int(thisDay.Month()), day)) {
+			sum += d
+		}
 	}
 	return float64(sum) / 60
 }
+
+// AvailableDaysThisMonth returns the total days that could be working days
+func AvailableDaysThisMonth(t time.Time, daysOff []string) int {
+	totalDays := 0
+	thisDay := t
+	lastDay := thisDay.Day()
+	// lastDayMonth := time.Date(thisDay.Year(), time.Month(int(thisDay.Month())+1), 0, 0, 0, 0, 0, time.UTC)
+	// lastDay := lastDayMonth.Day()
+
+	for i := 1; i <= lastDay; i++ {
+		currDay := time.Date(thisDay.Year(), time.Month(int(thisDay.Month())), i, 0, 0, 0, 0, time.UTC)
+		if isDayOff(daysOff, currDay.Format("2006-01-02")) {
+			continue
+		}
+		if int(currDay.Weekday()) == 0 || int(currDay.Weekday()) == 6 {
+			continue
+		}
+		totalDays++
+	}
+
+	return totalDays
+}
+
+func isDayOff(daysOff []string, day string) bool {
+	for _, d := range daysOff {
+		if d == day {
+			return true
+		}
+	}
+	return false
+}
diff --git a/pkg/reporting/simple_test.go b/pkg/reporting/simple_test.go
index ae069be..a8d5413 100644
--- a/pkg/reporting/simple_test.go
+++ b/pkg/reporting/simple_test.go
@@ -55,6 +55,7 @@ func Test_sumThisMonth(t *testing.T) {
 		name string
 		data Years
 		t    time.Time
+		off  []string
 		want float64
 	}{
 		{
@@ -87,12 +88,54 @@ func Test_sumThisMonth(t *testing.T) {
 			t:    dec,
 			want: 660 / 60,
 		},
+		{
+			name: "two days, one off",
+			data: Years{"2020": {"December": {"30": 1440, "31": 1443}}},
+			t:    dec,
+			off:  []string{"2020-12-31"},
+			want: 1440.0 / 60,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if got := sumThisMonth(tt.data, tt.t); got != tt.want {
+			if got := sumThisMonth(tt.data, tt.t, tt.off); got != tt.want {
 				t.Errorf("sumThisMonth() = %v, want %v", got, tt.want)
 			}
 		})
 	}
 }
+
+func Test_workingDays(t *testing.T) {
+	dec, _ := time.Parse("2006-01-02 15:04", "2020-12-31 9:59")
+	jan, _ := time.Parse("2006-01-02 15:04", "2021-01-02 9:59")
+	tests := []struct {
+		name string
+		t    time.Time
+		off  []string
+		want int
+	}{
+		{
+			name: "last day of month",
+			t:    dec,
+			want: 23,
+		},
+		{
+			name: "2nd day of month is Saturday",
+			t:    jan,
+			want: 1,
+		},
+		{
+			name: "last day of month, two days off",
+			t:    dec,
+			off:  []string{"2020-12-25", "2020-12-31"},
+			want: 21,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := AvailableDaysThisMonth(tt.t, tt.off); got != tt.want {
+				t.Errorf("workingDays() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}