diff --git a/cmd/restic/cmd_forget.go b/cmd/restic/cmd_forget.go
index 4debaef3b..4afef1380 100644
--- a/cmd/restic/cmd_forget.go
+++ b/cmd/restic/cmd_forget.go
@@ -27,14 +27,14 @@ data after 'forget' was run successfully, see the 'prune' command. `,
 
 // ForgetOptions collects all options for the forget command.
 type ForgetOptions struct {
-	Last       int
-	Hourly     int
-	Daily      int
-	Weekly     int
-	Monthly    int
-	Yearly     int
-	WithinDays int
-	KeepTags   restic.TagLists
+	Last     int
+	Hourly   int
+	Daily    int
+	Weekly   int
+	Monthly  int
+	Yearly   int
+	Within   restic.Duration
+	KeepTags restic.TagLists
 
 	Host    string
 	Tags    restic.TagLists
@@ -59,7 +59,7 @@ func init() {
 	f.IntVarP(&forgetOptions.Weekly, "keep-weekly", "w", 0, "keep the last `n` weekly snapshots")
 	f.IntVarP(&forgetOptions.Monthly, "keep-monthly", "m", 0, "keep the last `n` monthly snapshots")
 	f.IntVarP(&forgetOptions.Yearly, "keep-yearly", "y", 0, "keep the last `n` yearly snapshots")
-	f.IntVar(&forgetOptions.WithinDays, "keep-within", 0, "keep snapshots that were created within `days` before the newest")
+	f.VarP(&forgetOptions.Within, "keep-within", "", "keep snapshots that were created within `duration` before the newest (e.g. 1y5m7d)")
 
 	f.Var(&forgetOptions.KeepTags, "keep-tag", "keep snapshots with this `taglist` (can be specified multiple times)")
 	// Sadly the commonly used shortcut `H` is already used.
@@ -172,7 +172,7 @@ func runForget(opts ForgetOptions, gopts GlobalOptions, args []string) error {
 		Weekly:  opts.Weekly,
 		Monthly: opts.Monthly,
 		Yearly:  opts.Yearly,
-		Within:  opts.WithinDays,
+		Within:  opts.Within,
 		Tags:    opts.KeepTags,
 	}
 
diff --git a/internal/restic/duration.go b/internal/restic/duration.go
new file mode 100644
index 000000000..09289849b
--- /dev/null
+++ b/internal/restic/duration.go
@@ -0,0 +1,131 @@
+package restic
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"unicode"
+
+	"github.com/restic/restic/internal/errors"
+)
+
+// Duration is similar to time.Duration, except it only supports larger ranges
+// like days, months, and years.
+type Duration struct {
+	Days, Months, Years int
+}
+
+func (d Duration) String() string {
+	var s string
+	if d.Years != 0 {
+		s += fmt.Sprintf("%dy", d.Years)
+	}
+
+	if d.Months != 0 {
+		s += fmt.Sprintf("%dm", d.Months)
+	}
+
+	if d.Days != 0 {
+		s += fmt.Sprintf("%dd", d.Days)
+	}
+
+	return s
+}
+
+func nextNumber(input string) (num int, rest string, err error) {
+	if len(input) == 0 {
+		return 0, "", nil
+	}
+
+	var (
+		n        string
+		negative bool
+	)
+
+	if input[0] == '-' {
+		negative = true
+		input = input[1:]
+	}
+
+	for i, s := range input {
+		if !unicode.IsNumber(s) {
+			rest = input[i:]
+			break
+		}
+
+		n += string(s)
+	}
+
+	if len(n) == 0 {
+		return 0, input, errors.New("no number found")
+	}
+
+	num, err = strconv.Atoi(n)
+	if err != nil {
+		panic(err)
+	}
+
+	if negative {
+		num = -num
+	}
+
+	return num, rest, nil
+}
+
+// ParseDuration parses a duration from a string. The format is:
+//    6y5m234d
+func ParseDuration(s string) (Duration, error) {
+	var (
+		d   Duration
+		num int
+		err error
+	)
+
+	s = strings.TrimSpace(s)
+
+	for s != "" {
+		num, s, err = nextNumber(s)
+		if err != nil {
+			return Duration{}, err
+		}
+
+		if len(s) == 0 {
+			return Duration{}, errors.Errorf("no unit found after number %d", num)
+		}
+
+		switch s[0] {
+		case 'y':
+			d.Years = num
+		case 'm':
+			d.Months = num
+		case 'd':
+			d.Days = num
+		}
+
+		s = s[1:]
+	}
+
+	return d, nil
+}
+
+// Set calls ParseDuration and updates d.
+func (d *Duration) Set(s string) error {
+	v, err := ParseDuration(s)
+	if err != nil {
+		return err
+	}
+
+	*d = v
+	return nil
+}
+
+// Type returns the type of Duration, usable within github.com/spf13/pflag and
+// in help texts.
+func (d Duration) Type() string {
+	return "duration"
+}
+
+// Zero returns true if the duration is empty (all values are set to zero).
+func (d Duration) Zero() bool {
+	return d.Years == 0 && d.Months == 0 && d.Days == 0
+}
diff --git a/internal/restic/duration_test.go b/internal/restic/duration_test.go
new file mode 100644
index 000000000..0d5306069
--- /dev/null
+++ b/internal/restic/duration_test.go
@@ -0,0 +1,82 @@
+package restic
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestNextNumber(t *testing.T) {
+	var tests = []struct {
+		input string
+		num   int
+		rest  string
+		err   bool
+	}{
+		{
+			input: "3d", num: 3, rest: "d",
+		},
+		{
+			input: "7m5d", num: 7, rest: "m5d",
+		},
+		{
+			input: "-23y7m5d", num: -23, rest: "y7m5d",
+		},
+		{
+			input: "  5d", num: 0, rest: "  5d", err: true,
+		},
+		{
+			input: "5d  ", num: 5, rest: "d  ",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			num, rest, err := nextNumber(test.input)
+
+			if err != nil && !test.err {
+				t.Fatal(err)
+			}
+
+			if num != test.num {
+				t.Errorf("wrong num, want %d, got %d", test.num, num)
+			}
+
+			if rest != test.rest {
+				t.Errorf("wrong rest, want %q, got %q", test.rest, rest)
+			}
+		})
+	}
+}
+
+func TestParseDuration(t *testing.T) {
+	var tests = []struct {
+		input  string
+		d      Duration
+		output string
+	}{
+		{"3d", Duration{Days: 3}, "3d"},
+		{"7m5d", Duration{Months: 7, Days: 5}, "7m5d"},
+		{"5d7m", Duration{Months: 7, Days: 5}, "7m5d"},
+		{"-7m5d", Duration{Months: -7, Days: 5}, "-7m5d"},
+		{"2y7m-5d", Duration{Years: 2, Months: 7, Days: -5}, "2y7m-5d"},
+	}
+
+	for _, test := range tests {
+		t.Run("", func(t *testing.T) {
+			d, err := ParseDuration(test.input)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !cmp.Equal(d, test.d) {
+				t.Error(cmp.Diff(test.d, d))
+			}
+
+			s := d.String()
+			if s != test.output {
+				t.Errorf("unexpected return of String(), want %q, got %q", test.output, s)
+			}
+		})
+	}
+}
diff --git a/internal/restic/snapshot_policy.go b/internal/restic/snapshot_policy.go
index 244c19140..df142c0fb 100644
--- a/internal/restic/snapshot_policy.go
+++ b/internal/restic/snapshot_policy.go
@@ -16,7 +16,7 @@ type ExpirePolicy struct {
 	Weekly  int       // keep the last n weekly snapshots
 	Monthly int       // keep the last n monthly snapshots
 	Yearly  int       // keep the last n yearly snapshots
-	Within  int       // keep snapshots made within this number of days since the newest snapshot
+	Within  Duration  // keep snapshots made within this duration
 	Tags    []TagList // keep all snapshots that include at least one of the tag lists.
 }
 
@@ -40,11 +40,26 @@ func (e ExpirePolicy) String() (s string) {
 	if e.Yearly > 0 {
 		keeps = append(keeps, fmt.Sprintf("%d yearly", e.Yearly))
 	}
-	if e.Within != 0 {
-		keeps = append(keeps, fmt.Sprintf("snapshots within %d days of the newest snapshot", e.Within))
+
+	if len(keeps) > 0 {
+		s = fmt.Sprintf("keep the last %s snapshots", strings.Join(keeps, ", "))
 	}
 
-	return fmt.Sprintf("keep the last %s snapshots", strings.Join(keeps, ", "))
+	if len(e.Tags) > 0 {
+		if s != "" {
+			s += " and "
+		}
+		s += fmt.Sprintf("all snapshots with tags %s", e.Tags)
+	}
+
+	if !e.Within.Zero() {
+		if s != "" {
+			s += " and "
+		}
+		s += fmt.Sprintf("all snapshots within %s of the newest", e.Within)
+	}
+
+	return s
 }
 
 // Sum returns the maximum number of snapshots to be kept according to this
@@ -149,8 +164,8 @@ func ApplyPolicy(list Snapshots, p ExpirePolicy) (keep, remove Snapshots) {
 		}
 
 		// If the timestamp of the snapshot is within the range, then keep it.
-		if p.Within != 0 {
-			t := latest.AddDate(0, 0, -p.Within)
+		if !p.Within.Zero() {
+			t := latest.AddDate(-p.Within.Years, -p.Within.Months, -p.Within.Days)
 			if cur.Time.After(t) {
 				keepSnap = true
 			}
diff --git a/internal/restic/snapshot_policy_test.go b/internal/restic/snapshot_policy_test.go
index 9aa5200f1..f2e0605e3 100644
--- a/internal/restic/snapshot_policy_test.go
+++ b/internal/restic/snapshot_policy_test.go
@@ -21,8 +21,8 @@ func parseTimeUTC(s string) time.Time {
 	return t.UTC()
 }
 
-func parseDuration(s string) time.Duration {
-	d, err := time.ParseDuration(s)
+func parseDuration(s string) restic.Duration {
+	d, err := restic.ParseDuration(s)
 	if err != nil {
 		panic(err)
 	}
@@ -180,10 +180,10 @@ var expireTests = []restic.ExpirePolicy{
 	{Tags: []restic.TagList{{"foo"}}},
 	{Tags: []restic.TagList{{"foo", "bar"}}},
 	{Tags: []restic.TagList{{"foo"}, {"bar"}}},
-	{Within: 1},
-	{Within: 2},
-	{Within: 7},
-	{Within: 30},
+	{Within: parseDuration("1d")},
+	{Within: parseDuration("2d")},
+	{Within: parseDuration("7d")},
+	{Within: parseDuration("1m")},
 }
 
 func TestApplyPolicy(t *testing.T) {