diff --git a/irc/accounts.go b/irc/accounts.go
index 375668cd..b9082083 100644
--- a/irc/accounts.go
+++ b/irc/accounts.go
@@ -378,7 +378,7 @@ func (am *AccountManager) Register(client *Client, account string, callbackNames
 		return err
 	}
 
-	registeredTimeStr := strconv.FormatInt(time.Now().Unix(), 10)
+	registeredTimeStr := strconv.FormatInt(time.Now().UnixNano(), 10)
 	callbackSpec := fmt.Sprintf("%s:%s", callbackNamespace, callbackValue)
 
 	var setOptions *buntdb.SetOptions
@@ -998,7 +998,7 @@ func (am *AccountManager) deserializeRawAccount(raw rawClientAccount, cfName str
 	result.Name = raw.Name
 	result.NameCasefolded = cfName
 	regTimeInt, _ := strconv.ParseInt(raw.RegisteredAt, 10, 64)
-	result.RegisteredAt = time.Unix(regTimeInt, 0).UTC()
+	result.RegisteredAt = time.Unix(0, regTimeInt).UTC()
 	e := json.Unmarshal([]byte(raw.Credentials), &result.Credentials)
 	if e != nil {
 		am.server.logger.Error("internal", "could not unmarshal credentials", e.Error())
diff --git a/irc/database.go b/irc/database.go
index 56068356..bd9bbafc 100644
--- a/irc/database.go
+++ b/irc/database.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"strconv"
 	"strings"
 	"time"
 
@@ -22,7 +23,7 @@ const (
 	// 'version' of the database schema
 	keySchemaVersion = "db.version"
 	// latest schema of the db
-	latestDbSchema = "9"
+	latestDbSchema = "10"
 )
 
 type SchemaChanger func(*Config, *buntdb.Tx) error
@@ -594,6 +595,32 @@ func schemaChangeV8ToV9(config *Config, tx *buntdb.Tx) error {
 	return nil
 }
 
+// #836: account registration time at nanosecond resolution
+// (mostly to simplify testing)
+func schemaChangeV9ToV10(config *Config, tx *buntdb.Tx) error {
+	prefix := "account.registered.time "
+	var accounts, times []string
+	tx.AscendGreaterOrEqual("", prefix, func(key, value string) bool {
+		if !strings.HasPrefix(key, prefix) {
+			return false
+		}
+		account := strings.TrimPrefix(key, prefix)
+		accounts = append(accounts, account)
+		times = append(times, value)
+		return true
+	})
+	for i, account := range accounts {
+		time, err := strconv.ParseInt(times[i], 10, 64)
+		if err != nil {
+			log.Printf("corrupt registration time entry for %s: %v\n", account, err)
+			continue
+		}
+		time = time * 1000000000
+		tx.Set(prefix+account, strconv.FormatInt(time, 10), nil)
+	}
+	return nil
+}
+
 func init() {
 	allChanges := []SchemaChange{
 		{
@@ -636,6 +663,11 @@ func init() {
 			TargetVersion:  "9",
 			Changer:        schemaChangeV8ToV9,
 		},
+		{
+			InitialVersion: "9",
+			TargetVersion:  "10",
+			Changer:        schemaChangeV9ToV10,
+		},
 	}
 
 	// build the index
diff --git a/irc/server.go b/irc/server.go
index c7007fe6..685e3423 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -919,14 +919,16 @@ func (server *Server) GetHistorySequence(providedChannel *Channel, client *Clien
 	if config.History.Restrictions.ExpireTime != 0 {
 		cutoff = time.Now().UTC().Add(-time.Duration(config.History.Restrictions.ExpireTime))
 	}
-	if config.History.Restrictions.EnforceRegistrationDate {
+	// #836: registration date cutoff is always enforced for DMs
+	if config.History.Restrictions.EnforceRegistrationDate || channel == nil {
 		regCutoff := client.historyCutoff()
 		// take the later of the two cutoffs
 		if regCutoff.After(cutoff) {
 			cutoff = regCutoff
 		}
 	}
-	if !cutoff.IsZero() {
+	// #836 again: grace period is never applied to DMs
+	if !cutoff.IsZero() && channel != nil {
 		cutoff = cutoff.Add(-time.Duration(config.History.Restrictions.GracePeriod))
 	}