diff --git a/2018/day04-1.go b/2018/day04-1.go
index 5c01886..59cd3b5 100644
--- a/2018/day04-1.go
+++ b/2018/day04-1.go
@@ -2,42 +2,39 @@ package main
 
 import (
 	"fmt"
-	"sort"
-	"strconv"
-	"strings"
-	"time"
 
+	"internal/guards"
 	"internal/util"
 )
 
 func main() {
 	data := util.ReadInput()
-	shifts := ParseInput(data)
-	guards := BuildGuards(shifts)
+	shifts := guards.ParseInput(data)
+	guards := guards.BuildGuards(shifts)
 
 	sleepiest, sleepiestMinute := FindSleepiestData(guards)
 
-	fmt.Printf("Sleepiest Guard: %d\n", sleepiest.id)
+	fmt.Printf("Sleepiest Guard: %d\n", sleepiest.ID)
 	fmt.Printf("Sleepiest Minute: %d\n", sleepiestMinute)
-	fmt.Printf("Result: %d\n", sleepiest.id*sleepiestMinute)
+	fmt.Printf("Result: %d\n", sleepiest.ID*sleepiestMinute)
 }
 
-func FindSleepiestData(guards map[int]*Guard) (*Guard, int) {
-	var sleepiest *Guard
-	for _, guard := range guards {
+func FindSleepiestData(data map[int]*guards.Guard) (*guards.Guard, int) {
+	var sleepiest *guards.Guard
+	for _, guard := range data {
 		if sleepiest == nil {
 			sleepiest = guard
 			continue
 		}
 
-		if guard.sleepTotal > sleepiest.sleepTotal {
+		if guard.SleepTotal > sleepiest.SleepTotal {
 			sleepiest = guard
 		}
 	}
 
 	sleepiestMinute := -1
 	sleepiestCount := 0
-	for minute, sleepiness := range sleepiest.sleep {
+	for minute, sleepiness := range sleepiest.Sleep {
 		if sleepiness > sleepiestCount {
 			sleepiestCount = sleepiness
 			sleepiestMinute = minute
@@ -46,95 +43,3 @@ func FindSleepiestData(guards map[int]*Guard) (*Guard, int) {
 
 	return sleepiest, sleepiestMinute
 }
-
-type Guard struct {
-	id         int
-	sleep      [60]int
-	sleepTotal int
-}
-
-type SleepEvent struct {
-	start, end int
-}
-
-type Shift struct {
-	start       time.Time
-	guard       int
-	sleepEvents []*SleepEvent
-}
-
-// ParseInput takes the input data and creates a series of "Shift" objects,
-// which are just a structured form of the data.
-func ParseInput(rawData []string) []*Shift {
-	sort.Strings(rawData)
-
-	shifts := []*Shift{}
-	var currentShift *Shift
-	var currentSleepEvent *SleepEvent
-
-	for _, line := range rawData {
-		data := strings.Split(line, "]")
-		timestamp, _ := time.Parse("2006-01-02 15:04", data[0][1:])
-		event := data[1][1:]
-
-		// handle beginning of shift
-		if strings.HasPrefix(event, "Guard #") {
-			// save old shift first
-			if currentShift != nil {
-				shifts = append(shifts, currentShift)
-			}
-
-			// now extract the guard ID and create a new Shift object
-			guardID, _ := strconv.Atoi(strings.Split(event, " ")[1][1:])
-			currentShift = &Shift{
-				guard: guardID,
-				start: timestamp,
-			}
-		}
-
-		if strings.HasPrefix(event, "falls") {
-			currentSleepEvent = &SleepEvent{
-				start: timestamp.Minute(),
-			}
-		}
-
-		if strings.HasPrefix(event, "wakes") {
-			currentSleepEvent.end = timestamp.Minute()
-			currentShift.sleepEvents = append(currentShift.sleepEvents, currentSleepEvent)
-		}
-	}
-
-	// save last shift
-	shifts = append(shifts, currentShift)
-
-	return shifts
-}
-
-// BuildGuards takes the shift data created by ParseInput and builds a map of
-// 'guards', with a per-minute counter (and handy sum) of their sleep habits.
-func BuildGuards(data []*Shift) map[int]*Guard {
-	guards := make(map[int]*Guard)
-
-	for _, shift := range data {
-		// fetch the guard for this shift, initialize if necessary
-		var guard *Guard
-		// declaring 'ok' here seems to be the only way to keep 'guard' from becoming
-		// a local variable inside the conditional. This seems like a flaw.
-		var ok bool
-		if guard, ok = guards[shift.guard]; !ok {
-			guard = &Guard{
-				id: shift.guard,
-			}
-			guards[guard.id] = guard
-		}
-
-		for _, event := range shift.sleepEvents {
-			guard.sleepTotal += event.end - event.start
-			for i := event.start; i < event.end; i++ {
-				guard.sleep[i]++
-			}
-		}
-	}
-
-	return guards
-}
diff --git a/2018/internal/guards/guards.go b/2018/internal/guards/guards.go
new file mode 100644
index 0000000..19c456e
--- /dev/null
+++ b/2018/internal/guards/guards.go
@@ -0,0 +1,100 @@
+package guards
+
+import (
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+type Guard struct {
+	ID         int
+	Sleep      [60]int
+	SleepTotal int
+}
+
+type SleepEvent struct {
+	start, end int
+}
+
+type Shift struct {
+	start       time.Time
+	guard       int
+	sleepEvents []*SleepEvent
+}
+
+// ParseInput takes the input data and creates a series of "Shift" objects,
+// which are just a structured form of the data.
+func ParseInput(rawData []string) []*Shift {
+	sort.Strings(rawData)
+
+	shifts := []*Shift{}
+	var currentShift *Shift
+	var currentSleepEvent *SleepEvent
+
+	for _, line := range rawData {
+		data := strings.Split(line, "]")
+		timestamp, _ := time.Parse("2006-01-02 15:04", data[0][1:])
+		event := data[1][1:]
+
+		// handle beginning of shift
+		if strings.HasPrefix(event, "Guard #") {
+			// save old shift first
+			if currentShift != nil {
+				shifts = append(shifts, currentShift)
+			}
+
+			// now extract the guard ID and create a new Shift object
+			guardID, _ := strconv.Atoi(strings.Split(event, " ")[1][1:])
+			currentShift = &Shift{
+				guard: guardID,
+				start: timestamp,
+			}
+		}
+
+		if strings.HasPrefix(event, "falls") {
+			currentSleepEvent = &SleepEvent{
+				start: timestamp.Minute(),
+			}
+		}
+
+		if strings.HasPrefix(event, "wakes") {
+			currentSleepEvent.end = timestamp.Minute()
+			currentShift.sleepEvents = append(currentShift.sleepEvents, currentSleepEvent)
+		}
+	}
+
+	// save last shift
+	shifts = append(shifts, currentShift)
+
+	return shifts
+}
+
+// BuildGuards takes the shift data created by ParseInput and builds a map of
+// 'guards', with a per-minute counter (and handy sum) of their sleep habits.
+func BuildGuards(data []*Shift) map[int]*Guard {
+	guards := make(map[int]*Guard)
+
+	for _, shift := range data {
+		// fetch the guard for this shift, initialize if necessary
+		var guard *Guard
+		// declaring 'ok' here seems to be the only way to keep 'guard' from becoming
+		// a local variable inside the conditional. This seems like a flaw.
+		var ok bool
+		if guard, ok = guards[shift.guard]; !ok {
+			guard = &Guard{
+				ID: shift.guard,
+			}
+			guards[guard.ID] = guard
+		}
+
+		for _, event := range shift.sleepEvents {
+			guard.SleepTotal += event.end - event.start
+			for i := event.start; i < event.end; i++ {
+				guard.Sleep[i]++
+			}
+		}
+	}
+
+	return guards
+}