diff --git a/models/issue.go b/models/issue.go
index 8d8c304666..0e6c794055 100644
--- a/models/issue.go
+++ b/models/issue.go
@@ -915,7 +915,10 @@ func Issues(opts *IssuesOptions) ([]*Issue, error) {
 	}
 
 	if len(opts.Labels) > 0 && opts.Labels != "0" {
-		labelIDs := base.StringsToInt64s(strings.Split(opts.Labels, ","))
+		labelIDs, err := base.StringsToInt64s(strings.Split(opts.Labels, ","))
+		if err != nil {
+			return nil, err
+		}
 		if len(labelIDs) > 0 {
 			sess.
 				Join("INNER", "issue_label", "issue.id = issue_label.issue_id").
@@ -1171,10 +1174,11 @@ func GetIssueStats(opts *IssueStatsOptions) *IssueStats {
 			And("is_pull = ?", opts.IsPull)
 
 		if len(opts.Labels) > 0 && opts.Labels != "0" {
-			labelIDs := base.StringsToInt64s(strings.Split(opts.Labels, ","))
-			if len(labelIDs) > 0 {
-				sess.
-					Join("INNER", "issue_label", "issue.id = issue_id").
+			labelIDs, err := base.StringsToInt64s(strings.Split(opts.Labels, ","))
+			if err != nil {
+				log.Warn("Malformed Labels argument: %s", opts.Labels)
+			} else if len(labelIDs) > 0 {
+				sess.Join("INNER", "issue_label", "issue.id = issue_id").
 					In("label_id", labelIDs)
 			}
 		}
diff --git a/modules/base/tool.go b/modules/base/tool.go
index eb25108869..cb2eafd309 100644
--- a/modules/base/tool.go
+++ b/modules/base/tool.go
@@ -56,6 +56,9 @@ func DetectEncoding(content []byte) (string, error) {
 	}
 
 	result, err := chardet.NewTextDetector().DetectBest(content)
+	if err != nil {
+		return "", err
+	}
 	if result.Charset != "UTF-8" && len(setting.Repository.AnsiCharset) > 0 {
 		log.Debug("Using default AnsiCharset: %s", setting.Repository.AnsiCharset)
 		return setting.Repository.AnsiCharset, err
@@ -256,19 +259,25 @@ func computeTimeDiff(diff int64) (int64, string) {
 		diffStr = "1 year"
 	default:
 		diffStr = fmt.Sprintf("%d years", diff/Year)
-		diff = 0
+		diff -= (diff / Year) * Year
 	}
 	return diff, diffStr
 }
 
 // TimeSincePro calculates the time interval and generate full user-friendly string.
 func TimeSincePro(then time.Time) string {
-	now := time.Now()
+	return timeSincePro(then, time.Now())
+}
+
+func timeSincePro(then, now time.Time) string {
 	diff := now.Unix() - then.Unix()
 
 	if then.After(now) {
 		return "future"
 	}
+	if diff == 0 {
+		return "now"
+	}
 
 	var timeStr, diffStr string
 	for {
@@ -282,9 +291,7 @@ func TimeSincePro(then time.Time) string {
 	return strings.TrimPrefix(timeStr, ", ")
 }
 
-func timeSince(then time.Time, lang string) string {
-	now := time.Now()
-
+func timeSince(then, now time.Time, lang string) string {
 	lbl := i18n.Tr(lang, "tool.ago")
 	diff := now.Unix() - then.Unix()
 	if then.After(now) {
@@ -295,7 +302,7 @@ func timeSince(then time.Time, lang string) string {
 	switch {
 	case diff <= 0:
 		return i18n.Tr(lang, "tool.now")
-	case diff <= 2:
+	case diff <= 1:
 		return i18n.Tr(lang, "tool.1s", lbl)
 	case diff < 1*Minute:
 		return i18n.Tr(lang, "tool.seconds", diff, lbl)
@@ -334,12 +341,18 @@ func timeSince(then time.Time, lang string) string {
 
 // RawTimeSince retrieves i18n key of time since t
 func RawTimeSince(t time.Time, lang string) string {
-	return timeSince(t, lang)
+	return timeSince(t, time.Now(), lang)
 }
 
 // TimeSince calculates the time interval and generate user-friendly string.
-func TimeSince(t time.Time, lang string) template.HTML {
-	return template.HTML(fmt.Sprintf(`<span class="time-since" title="%s">%s</span>`, t.Format(setting.TimeFormat), timeSince(t, lang)))
+func TimeSince(then time.Time, lang string) template.HTML {
+	return htmlTimeSince(then, time.Now(), lang)
+}
+
+func htmlTimeSince(then, now time.Time, lang string) template.HTML {
+	return template.HTML(fmt.Sprintf(`<span class="time-since" title="%s">%s</span>`,
+		then.Format(setting.TimeFormat),
+		timeSince(then, now, lang)))
 }
 
 // Storage space size types
@@ -424,10 +437,10 @@ func Subtract(left interface{}, right interface{}) interface{} {
 	case int64:
 		rright = right.(int64)
 	case float32:
-		fright = float64(left.(float32))
+		fright = float64(right.(float32))
 		isInt = false
 	case float64:
-		fleft = left.(float64)
+		fright = right.(float64)
 		isInt = false
 	}
 
@@ -459,12 +472,16 @@ func TruncateString(str string, limit int) string {
 }
 
 // StringsToInt64s converts a slice of string to a slice of int64.
-func StringsToInt64s(strs []string) []int64 {
+func StringsToInt64s(strs []string) ([]int64, error) {
 	ints := make([]int64, len(strs))
 	for i := range strs {
-		ints[i] = com.StrTo(strs[i]).MustInt64()
+		n, err := com.StrTo(strs[i]).Int64()
+		if err != nil {
+			return ints, err
+		}
+		ints[i] = n
 	}
-	return ints
+	return ints, nil
 }
 
 // Int64sToStrings converts a slice of int64 to a slice of string.
diff --git a/modules/base/tool_test.go b/modules/base/tool_test.go
index 2ca70b8b32..9c4fb89e8e 100644
--- a/modules/base/tool_test.go
+++ b/modules/base/tool_test.go
@@ -4,10 +4,40 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/modules/setting"
+	"github.com/Unknwon/i18n"
+	macaroni18n "github.com/go-macaron/i18n"
 	"github.com/stretchr/testify/assert"
+	"os"
 	"strk.kbt.io/projects/go/libravatar"
+	"time"
 )
 
+var BaseDate time.Time
+
+// time durations
+const (
+	DayDur   = 24 * time.Hour
+	WeekDur  = 7 * DayDur
+	MonthDur = 30 * DayDur
+	YearDur  = 12 * MonthDur
+)
+
+func TestMain(m *testing.M) {
+	// setup
+	macaroni18n.I18n(macaroni18n.Options{
+		Directory:   "../../conf/locale/",
+		DefaultLang: "en-US",
+		Langs:       []string{"en-US"},
+		Names:       []string{"english"},
+	})
+	BaseDate = time.Date(2000, time.January, 1, 0, 0, 0, 0, time.UTC)
+
+	// run the tests
+	retVal := m.Run()
+
+	os.Exit(retVal)
+}
+
 func TestEncodeMD5(t *testing.T) {
 	assert.Equal(t,
 		"3858f62230ac3c915f300c664312c63f",
@@ -26,7 +56,36 @@ func TestShortSha(t *testing.T) {
 	assert.Equal(t, "veryverylo", ShortSha("veryverylong"))
 }
 
-// TODO: Test DetectEncoding()
+func TestDetectEncoding(t *testing.T) {
+	testSuccess := func(b []byte, expected string) {
+		encoding, err := DetectEncoding(b)
+		assert.NoError(t, err)
+		assert.Equal(t, expected, encoding)
+	}
+	// utf-8
+	b := []byte("just some ascii")
+	testSuccess(b, "UTF-8")
+
+	// utf-8-sig: "hey" (with BOM)
+	b = []byte{0xef, 0xbb, 0xbf, 0x68, 0x65, 0x79}
+	testSuccess(b, "UTF-8")
+
+	// utf-16: "hey<accented G>"
+	b = []byte{0xff, 0xfe, 0x68, 0x00, 0x65, 0x00, 0x79, 0x00, 0xf4, 0x01}
+	testSuccess(b, "UTF-16LE")
+
+	// iso-8859-1: d<accented e>cor<newline>
+	b = []byte{0x44, 0xe9, 0x63, 0x6f, 0x72, 0x0a}
+	testSuccess(b, "ISO-8859-1")
+
+	setting.Repository.AnsiCharset = "placeholder"
+	testSuccess(b, "placeholder")
+
+	// invalid bytes
+	b = []byte{0xfa}
+	_, err := DetectEncoding(b)
+	assert.Error(t, err)
+}
 
 func TestBasicAuthDecode(t *testing.T) {
 	_, _, err := BasicAuthDecode("?")
@@ -88,11 +147,112 @@ func TestAvatarLink(t *testing.T) {
 	)
 }
 
-// TODO: computeTimeDiff()
-// TODO: TimeSincePro()
-// TODO: timeSince()
-// TODO: RawTimeSince()
-// TODO: TimeSince()
+func TestComputeTimeDiff(t *testing.T) {
+	// test that for each offset in offsets,
+	// computeTimeDiff(base + offset) == (offset, str)
+	test := func(base int64, str string, offsets ...int64) {
+		for _, offset := range offsets {
+			diff, diffStr := computeTimeDiff(base + offset)
+			assert.Equal(t, offset, diff)
+			assert.Equal(t, str, diffStr)
+		}
+	}
+	test(0, "now", 0)
+	test(1, "1 second", 0)
+	test(2, "2 seconds", 0)
+	test(Minute, "1 minute", 0, 1, 30, Minute-1)
+	test(2*Minute, "2 minutes", 0, Minute-1)
+	test(Hour, "1 hour", 0, 1, Hour-1)
+	test(5*Hour, "5 hours", 0, Hour-1)
+	test(Day, "1 day", 0, 1, Day-1)
+	test(5*Day, "5 days", 0, Day-1)
+	test(Week, "1 week", 0, 1, Week-1)
+	test(3*Week, "3 weeks", 0, 4*Day+25000)
+	test(Month, "1 month", 0, 1, Month-1)
+	test(10*Month, "10 months", 0, Month-1)
+	test(Year, "1 year", 0, Year-1)
+	test(3*Year, "3 years", 0, Year-1)
+}
+
+func TestTimeSince(t *testing.T) {
+	assert.Equal(t, "now", timeSince(BaseDate, BaseDate, "en"))
+
+	// test that each diff in `diffs` yields the expected string
+	test := func(expected string, diffs ...time.Duration) {
+		ago := i18n.Tr("en", "tool.ago")
+		fromNow := i18n.Tr("en", "tool.from_now")
+		for _, diff := range diffs {
+			actual := timeSince(BaseDate, BaseDate.Add(diff), "en")
+			assert.Equal(t, expected+" "+ago, actual)
+			actual = timeSince(BaseDate.Add(diff), BaseDate, "en")
+			assert.Equal(t, expected+" "+fromNow, actual)
+		}
+	}
+	test("1 second", time.Second, time.Second+50*time.Millisecond)
+	test("2 seconds", 2*time.Second, 2*time.Second+50*time.Millisecond)
+	test("1 minute", time.Minute, time.Minute+30*time.Second)
+	test("2 minutes", 2*time.Minute, 2*time.Minute+30*time.Second)
+	test("1 hour", time.Hour, time.Hour+30*time.Minute)
+	test("2 hours", 2*time.Hour, 2*time.Hour+30*time.Minute)
+	test("1 day", DayDur, DayDur+12*time.Hour)
+	test("2 days", 2*DayDur, 2*DayDur+12*time.Hour)
+	test("1 week", WeekDur, WeekDur+3*DayDur)
+	test("2 weeks", 2*WeekDur, 2*WeekDur+3*DayDur)
+	test("1 month", MonthDur, MonthDur+15*DayDur)
+	test("2 months", 2*MonthDur, 2*MonthDur+15*DayDur)
+	test("1 year", YearDur, YearDur+6*MonthDur)
+	test("2 years", 2*YearDur, 2*YearDur+6*MonthDur)
+}
+
+func TestTimeSincePro(t *testing.T) {
+	assert.Equal(t, "now", timeSincePro(BaseDate, BaseDate))
+
+	// test that a difference of `diff` yields the expected string
+	test := func(expected string, diff time.Duration) {
+		actual := timeSincePro(BaseDate, BaseDate.Add(diff))
+		assert.Equal(t, expected, actual)
+		assert.Equal(t, "future", timeSincePro(BaseDate.Add(diff), BaseDate))
+	}
+	test("1 second", time.Second)
+	test("2 seconds", 2*time.Second)
+	test("1 minute", time.Minute)
+	test("1 minute, 1 second", time.Minute+time.Second)
+	test("1 minute, 59 seconds", time.Minute+59*time.Second)
+	test("2 minutes", 2*time.Minute)
+	test("1 hour", time.Hour)
+	test("1 hour, 1 second", time.Hour+time.Second)
+	test("1 hour, 59 minutes, 59 seconds", time.Hour+59*time.Minute+59*time.Second)
+	test("2 hours", 2*time.Hour)
+	test("1 day", DayDur)
+	test("1 day, 23 hours, 59 minutes, 59 seconds",
+		DayDur+23*time.Hour+59*time.Minute+59*time.Second)
+	test("2 days", 2*DayDur)
+	test("1 week", WeekDur)
+	test("2 weeks", 2*WeekDur)
+	test("1 month", MonthDur)
+	test("3 months", 3*MonthDur)
+	test("1 year", YearDur)
+	test("2 years, 3 months, 1 week, 2 days, 4 hours, 12 minutes, 17 seconds",
+		2*YearDur+3*MonthDur+WeekDur+2*DayDur+4*time.Hour+
+			12*time.Minute+17*time.Second)
+}
+
+func TestHtmlTimeSince(t *testing.T) {
+	setting.TimeFormat = time.UnixDate
+	// test that `diff` yields a result containing `expected`
+	test := func(expected string, diff time.Duration) {
+		actual := htmlTimeSince(BaseDate, BaseDate.Add(diff), "en")
+		assert.Contains(t, actual, `title="Sat Jan  1 00:00:00 UTC 2000"`)
+		assert.Contains(t, actual, expected)
+	}
+	test("1 second", time.Second)
+	test("3 minutes", 3*time.Minute+5*time.Second)
+	test("1 day", DayDur+18*time.Hour)
+	test("1 week", WeekDur+6*DayDur)
+	test("3 months", 3*MonthDur+3*WeekDur)
+	test("2 years", 2*YearDur)
+	test("3 years", 3*YearDur+11*MonthDur+4*WeekDur)
+}
 
 func TestFileSize(t *testing.T) {
 	var size int64
@@ -108,11 +268,48 @@ func TestFileSize(t *testing.T) {
 	assert.Equal(t, "512TB", FileSize(size))
 	size = size * 1024
 	assert.Equal(t, "512PB", FileSize(size))
-	//size = size * 1024 TODO: Fix bug for EB
-	//assert.Equal(t, "512EB", FileSize(size))
+	size = size * 4
+	assert.Equal(t, "2.0EB", FileSize(size))
 }
 
-// TODO: Subtract()
+func TestSubtract(t *testing.T) {
+	toFloat64 := func(n interface{}) float64 {
+		switch n.(type) {
+		case int:
+			return float64(n.(int))
+		case int8:
+			return float64(n.(int8))
+		case int16:
+			return float64(n.(int16))
+		case int32:
+			return float64(n.(int32))
+		case int64:
+			return float64(n.(int64))
+		case float32:
+			return float64(n.(float32))
+		case float64:
+			return n.(float64)
+		default:
+			return 0.0
+		}
+	}
+	values := []interface{}{
+		int(-3),
+		int8(14),
+		int16(81),
+		int32(-156),
+		int64(1528),
+		float32(3.5),
+		float64(-15.348),
+	}
+	for _, left := range values {
+		for _, right := range values {
+			expected := toFloat64(left) - toFloat64(right)
+			sub := Subtract(left, right)
+			assert.InDelta(t, expected, sub, 1e-3)
+		}
+	}
+}
 
 func TestEllipsisString(t *testing.T) {
 	assert.Equal(t, "...", EllipsisString("foobar", 0))
@@ -137,14 +334,18 @@ func TestTruncateString(t *testing.T) {
 }
 
 func TestStringsToInt64s(t *testing.T) {
-	assert.Equal(t, []int64{}, StringsToInt64s([]string{}))
-	assert.Equal(t,
-		[]int64{1, 4, 16, 64, 256},
-		StringsToInt64s([]string{"1", "4", "16", "64", "256"}),
-	)
+	testSuccess := func(input []string, expected []int64) {
+		result, err := StringsToInt64s(input)
+		assert.NoError(t, err)
+		assert.Equal(t, expected, result)
+	}
+	testSuccess([]string{}, []int64{})
+	testSuccess([]string{"-1234"}, []int64{-1234})
+	testSuccess([]string{"1", "4", "16", "64", "256"},
+		[]int64{1, 4, 16, 64, 256})
 
-	// TODO: StringsToInt64s should return ([]int64, error)
-	assert.Equal(t, []int64{-1, 0, 0}, StringsToInt64s([]string{"-1", "a", "$"}))
+	_, err := StringsToInt64s([]string{"-1", "a", "$"})
+	assert.Error(t, err)
 }
 
 func TestInt64sToStrings(t *testing.T) {
diff --git a/routers/repo/issue.go b/routers/repo/issue.go
index e3c088d940..343b93e273 100644
--- a/routers/repo/issue.go
+++ b/routers/repo/issue.go
@@ -374,7 +374,10 @@ func ValidateRepoMetas(ctx *context.Context, form auth.CreateIssueForm) ([]int64
 	}
 
 	// Check labels.
-	labelIDs := base.StringsToInt64s(strings.Split(form.LabelIDs, ","))
+	labelIDs, err := base.StringsToInt64s(strings.Split(form.LabelIDs, ","))
+	if err != nil {
+		return nil, 0, 0
+	}
 	labelIDMark := base.Int64sToMap(labelIDs)
 	hasSelected := false
 	for i := range labels {