diff --git a/irc/custime/parseduration.go b/irc/custime/parseduration.go
new file mode 100644
index 00000000..7f18aad5
--- /dev/null
+++ b/irc/custime/parseduration.go
@@ -0,0 +1,183 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+
+package custime
+
+import (
+	"errors"
+	"time"
+)
+
+// see https://github.com/golang/go/blob/7ad512e7ffe576c4894ea84b02e954846fbda643/src/time/format.go#L1251
+
+// This is a forked version of the ParseDuration function that also handles days/months/years
+
+var errLeadingInt = errors.New("time: bad [0-9]*") // never printed
+
+// leadingInt consumes the leading [0-9]* from s.
+func leadingInt(s string) (x int64, rem string, err error) {
+	i := 0
+	for ; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			break
+		}
+		if x > (1<<63-1)/10 {
+			// overflow
+			return 0, "", errLeadingInt
+		}
+		x = x*10 + int64(c) - '0'
+		if x < 0 {
+			// overflow
+			return 0, "", errLeadingInt
+		}
+	}
+	return x, s[i:], nil
+}
+
+// leadingFraction consumes the leading [0-9]* from s.
+// It is used only for fractions, so does not return an error on overflow,
+// it just stops accumulating precision.
+func leadingFraction(s string) (x int64, scale float64, rem string) {
+	i := 0
+	scale = 1
+	overflow := false
+	for ; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			break
+		}
+		if overflow {
+			continue
+		}
+		if x > (1<<63-1)/10 {
+			// It's possible for overflow to give a positive number, so take care.
+			overflow = true
+			continue
+		}
+		y := x*10 + int64(c) - '0'
+		if y < 0 {
+			overflow = true
+			continue
+		}
+		x = y
+		scale *= 10
+	}
+	return x, scale, s[i:]
+}
+
+var unitMap = map[string]int64{
+	"ns": int64(time.Nanosecond),
+	"us": int64(time.Microsecond),
+	"µs": int64(time.Microsecond), // U+00B5 = micro symbol
+	"μs": int64(time.Microsecond), // U+03BC = Greek letter mu
+	"ms": int64(time.Millisecond),
+	"s":  int64(time.Second),
+	"m":  int64(time.Minute),
+	"h":  int64(time.Hour),
+	"d":  int64(time.Hour * 24),
+	"mo": int64(time.Hour * 24 * 30),
+	"y":  int64(time.Hour * 24 * 265),
+}
+
+// ParseDuration parses a duration string.
+// A duration string is a possibly signed sequence of
+// decimal numbers, each with optional fraction and a unit suffix,
+// such as "300ms", "-1.5h" or "2h45m".
+// Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
+func ParseDuration(s string) (time.Duration, error) {
+	// [-+]?([0-9]*(\.[0-9]*)?[a-z]+)+
+	orig := s
+	var d int64
+	neg := false
+
+	// Consume [-+]?
+	if s != "" {
+		c := s[0]
+		if c == '-' || c == '+' {
+			neg = c == '-'
+			s = s[1:]
+		}
+	}
+	// Special case: if all that is left is "0", this is zero.
+	if s == "0" {
+		return 0, nil
+	}
+	if s == "" {
+		return 0, errors.New("time: invalid duration " + orig)
+	}
+	for s != "" {
+		var (
+			v, f  int64       // integers before, after decimal point
+			scale float64 = 1 // value = v + f/scale
+		)
+
+		var err error
+
+		// The next character must be [0-9.]
+		if !(s[0] == '.' || '0' <= s[0] && s[0] <= '9') {
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+		// Consume [0-9]*
+		pl := len(s)
+		v, s, err = leadingInt(s)
+		if err != nil {
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+		pre := pl != len(s) // whether we consumed anything before a period
+
+		// Consume (\.[0-9]*)?
+		post := false
+		if s != "" && s[0] == '.' {
+			s = s[1:]
+			pl := len(s)
+			f, scale, s = leadingFraction(s)
+			post = pl != len(s)
+		}
+		if !pre && !post {
+			// no digits (e.g. ".s" or "-.s")
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+
+		// Consume unit.
+		i := 0
+		for ; i < len(s); i++ {
+			c := s[i]
+			if c == '.' || '0' <= c && c <= '9' {
+				break
+			}
+		}
+		if i == 0 {
+			return 0, errors.New("time: missing unit in duration " + orig)
+		}
+		u := s[:i]
+		s = s[i:]
+		unit, ok := unitMap[u]
+		if !ok {
+			return 0, errors.New("time: unknown unit " + u + " in duration " + orig)
+		}
+		if v > (1<<63-1)/unit {
+			// overflow
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+		v *= unit
+		if f > 0 {
+			// float64 is needed to be nanosecond accurate for fractions of hours.
+			// v >= 0 && (f*unit/scale) <= 3.6e+12 (ns/h, h is the largest unit)
+			v += int64(float64(f) * (float64(unit) / scale))
+			if v < 0 {
+				// overflow
+				return 0, errors.New("time: invalid duration " + orig)
+			}
+		}
+		d += v
+		if d < 0 {
+			// overflow
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+	}
+
+	if neg {
+		d = -d
+	}
+	return time.Duration(d), nil
+}
diff --git a/irc/dline.go b/irc/dline.go
index c92b2b67..b3088879 100644
--- a/irc/dline.go
+++ b/irc/dline.go
@@ -14,6 +14,7 @@ import (
 	"encoding/json"
 
 	"github.com/DanielOaks/girc-go/ircmsg"
+	"github.com/DanielOaks/oragono/irc/custime"
 	"github.com/tidwall/buntdb"
 )
 
@@ -201,7 +202,7 @@ func dlineHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 	}
 
 	// duration
-	duration, err := time.ParseDuration(msg.Params[currentArg])
+	duration, err := custime.ParseDuration(msg.Params[currentArg])
 	durationIsUsed := err == nil
 	if durationIsUsed {
 		currentArg++
diff --git a/irc/help.go b/irc/help.go
index 23751a2f..5d0fa284 100644
--- a/irc/help.go
+++ b/irc/help.go
@@ -112,7 +112,7 @@ Bans are saved across subsequent launches of the server.
 from. If "MYSELF" is not given, trying to DLINE yourself will result in an error.
 
 [duration] can be of the following forms:
-	10h 8m 13s
+	1y 12mo 31d 10h 8m 13s
 
 <net> is specified in typical CIDR notation. For example:
 	127.0.0.1/8
@@ -172,7 +172,7 @@ Bans are saved across subsequent launches of the server.
 from. If "MYSELF" is not given, trying to KLINE yourself will result in an error.
 
 [duration] can be of the following forms:
-	10h 8m 13s
+	1y 12mo 31d 10h 8m 13s
 
 <mask> is specified in typical IRC format. For example:
 	dan
diff --git a/irc/kline.go b/irc/kline.go
index 78ac8208..268ffa0a 100644
--- a/irc/kline.go
+++ b/irc/kline.go
@@ -11,6 +11,7 @@ import (
 
 	"github.com/DanielOaks/girc-go/ircmatch"
 	"github.com/DanielOaks/girc-go/ircmsg"
+	"github.com/DanielOaks/oragono/irc/custime"
 	"github.com/tidwall/buntdb"
 )
 
@@ -128,7 +129,7 @@ func klineHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 	}
 
 	// duration
-	duration, err := time.ParseDuration(msg.Params[currentArg])
+	duration, err := custime.ParseDuration(msg.Params[currentArg])
 	durationIsUsed := err == nil
 	if durationIsUsed {
 		currentArg++