diff --git a/aoc.go b/aoc.go
index 38acead..14032e2 100644
--- a/aoc.go
+++ b/aoc.go
@@ -2,9 +2,8 @@ package aoc
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strconv"
 	"time"
@@ -18,10 +17,10 @@ type AoC struct {
 
 func NewAoC(boardId, session string) (*AoC, error) {
 	if boardId == "" {
-		return nil, errors.New("Board ID is required")
+		return nil, new(BoardIdRequiredError)
 	}
 	if session == "" {
-		return nil, errors.New("Session key is required")
+		return nil, new(SessionRequiredError)
 	}
 	return &AoC{
 		session: session,
@@ -30,19 +29,29 @@ func NewAoC(boardId, session string) (*AoC, error) {
 	}, nil
 }
 
+func (a *AoC) SetCachedLeaderboard(l *Leaderboard) error {
+	yr, err := strconv.Atoi(l.Event)
+	if err != nil {
+		return new(InvalidYearError)
+	}
+
+	a.boards[yr] = l
+	return nil
+}
+
 func (a *AoC) GetCachedLeaderboard(year int) (*Leaderboard, error) {
 	if year < 2015 || year > time.Now().Year() {
-		return nil, errors.New("Invalid Year")
+		return nil, new(InvalidYearError)
 	}
 	if board, ok := a.boards[year]; ok {
 		return board, nil
 	}
-	return nil, errors.New(fmt.Sprintf("Leaderboard (%d) is not cached", year))
+	return nil, LeaderboardNotCachedError{year: year}
 }
 
 func (a *AoC) GetLeaderboard(year int) (*Leaderboard, error) {
 	if year < 2015 || year > time.Now().Year() {
-		return nil, errors.New("Invalid Year")
+		return nil, new(InvalidYearError)
 	}
 	if board, ok := a.boards[year]; ok {
 		if time.Since(board.LastFetch) < (time.Minute * 15) {
@@ -53,7 +62,7 @@ func (a *AoC) GetLeaderboard(year int) (*Leaderboard, error) {
 	a.boards[year], err = a.fetchLeaderboard(year)
 	if err != nil {
 		if err.Error() == "invalid character '<' looking for beginning of value" {
-			return nil, errors.New("Invalid Session Cookie")
+			return nil, new(SessionError)
 		}
 		return nil, err
 	}
@@ -77,17 +86,15 @@ func (a *AoC) fetchLeaderboard(year int) (*Leaderboard, error) {
 		return nil, err
 	}
 	defer resp.Body.Close()
-	body, err = ioutil.ReadAll(resp.Body)
+	body, err = io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
 	}
 	strBody := string(body)
-	//strBody = strings.ReplaceAll(strBody, "\"last_star_ts\":\"0\"", "\"last_star_ts\":0")
+	// strBody = strings.ReplaceAll(strBody, "\"last_star_ts\":\"0\"", "\"last_star_ts\":0")
 	err = json.Unmarshal([]byte(strBody), &leaderboard)
 	if err != nil {
-		fmt.Println("Error parsing board")
-		fmt.Println(err)
-		return nil, err
+		return nil, fmt.Errorf("error parsing board: %w", err)
 	}
 	for k, mbr := range leaderboard.Members {
 		starTs, err := strconv.ParseInt(mbr.RawStarTs, 10, 64)
@@ -144,7 +151,6 @@ func (a ByStarsThenScore) Less(i, j int) bool {
 }
 
 func (m *Member) UnmarshalJSON(data []byte) error {
-
 	var v map[string]interface{}
 	var err error
 
diff --git a/aoc_errors.go b/aoc_errors.go
new file mode 100644
index 0000000..b9cbd6c
--- /dev/null
+++ b/aoc_errors.go
@@ -0,0 +1,35 @@
+package aoc
+
+import "fmt"
+
+type SessionRequiredError struct{}
+
+func (e SessionRequiredError) Error() string {
+	return "session key is required"
+}
+
+type SessionError struct{}
+
+func (e SessionError) Error() string {
+	return "invalid session"
+}
+
+type BoardIdRequiredError struct{}
+
+func (e BoardIdRequiredError) Error() string {
+	return "board id is required"
+}
+
+type InvalidYearError struct{}
+
+func (e InvalidYearError) Error() string {
+	return "invalid year"
+}
+
+type LeaderboardNotCachedError struct {
+	year int
+}
+
+func (e LeaderboardNotCachedError) Error() string {
+	return fmt.Sprintf("leaderboard (%d) is not cached", e.year)
+}