diff --git a/wavesrv/pkg/telemetry/telemetry.go b/wavesrv/pkg/telemetry/telemetry.go
index 865d949aa..a8418aa06 100644
--- a/wavesrv/pkg/telemetry/telemetry.go
+++ b/wavesrv/pkg/telemetry/telemetry.go
@@ -6,7 +6,10 @@ package telemetry
 import (
 	"context"
 	"database/sql/driver"
+	"fmt"
 	"log"
+	"regexp"
+	"strconv"
 	"time"
 
 	"github.com/wavetermdev/waveterm/wavesrv/pkg/dbutil"
@@ -81,6 +84,99 @@ func GetCurDayStr() string {
 	return dayStr
 }
 
+func GetRelDayStr(relDays int) string {
+	now := time.Now()
+	dayStr := now.AddDate(0, 0, relDays).Format("2006-01-02")
+	return dayStr
+}
+
+// accepts a custom format string to return a daystr
+// can be either a prefix, a delta, or a prefix w/ a delta
+// if no prefix is given, "today" is assumed
+// examples: today-2d, bow, bom+1m-1d (that's end of the month), 2024-04-01+1w
+//
+// prefixes:
+//
+//	yyyy-mm-dd
+//	today
+//	yesterday
+//	bom (beginning of month)
+//	bow (beginning of week -- sunday)
+//
+// deltas:
+//
+//	+[n]d, -[n]d (e.g. +1d, -5d)
+//	+[n]w, -[n]w (e.g. +2w)
+//	+[n]m, -[n]m (e.g. -1m)
+//	deltas can be combined e.g. +1w-2d
+func GetCustomDayStr(format string) (string, error) {
+	m := customDayStrRe.FindStringSubmatch(format)
+	if m == nil {
+		return "", fmt.Errorf("invalid daystr format")
+	}
+	prefix, deltas := m[1], m[2]
+	if prefix == "" {
+		prefix = "today"
+	}
+	var rtnTime time.Time
+	now := time.Now()
+	switch prefix {
+	case "today":
+		rtnTime = now
+	case "yesterday":
+		rtnTime = now.AddDate(0, 0, -1)
+	case "bom":
+		rtnTime = time.Date(now.Year(), now.Month(), 1, 0, 0, 0, 0, now.Location())
+	case "bow":
+		weekday := now.Weekday()
+		if weekday == time.Sunday {
+			rtnTime = now
+		} else {
+			rtnTime = now.AddDate(0, 0, -int(weekday))
+		}
+	default:
+		m = daystrRe.FindStringSubmatch(prefix)
+		if m == nil {
+			return "", fmt.Errorf("invalid prefix format")
+		}
+		year, month, day := m[1], m[2], m[3]
+		yearInt, monthInt, dayInt := atoiNoErr(year), atoiNoErr(month), atoiNoErr(day)
+		if yearInt == 0 || monthInt == 0 || dayInt == 0 {
+			return "", fmt.Errorf("invalid prefix format")
+		}
+		rtnTime = time.Date(yearInt, time.Month(monthInt), dayInt, 0, 0, 0, 0, now.Location())
+	}
+	for _, delta := range regexp.MustCompile(`[+-]\d+[dwm]`).FindAllString(deltas, -1) {
+		deltaVal, err := strconv.Atoi(delta[1 : len(delta)-1])
+		if err != nil {
+			return "", fmt.Errorf("invalid delta format")
+		}
+		if delta[0] == '-' {
+			deltaVal = -deltaVal
+		}
+		switch delta[len(delta)-1] {
+		case 'd':
+			rtnTime = rtnTime.AddDate(0, 0, deltaVal)
+		case 'w':
+			rtnTime = rtnTime.AddDate(0, 0, deltaVal*7)
+		case 'm':
+			rtnTime = rtnTime.AddDate(0, deltaVal, 0)
+		}
+	}
+	return rtnTime.Format("2006-01-02"), nil
+}
+
+func atoiNoErr(str string) int {
+	val, err := strconv.Atoi(str)
+	if err != nil {
+		return 0
+	}
+	return val
+}
+
+var customDayStrRe = regexp.MustCompile(`^((?:\d{4}-\d{2}-\d{2})|today|yesterday|bom|bow)?((?:[+-]\d+[dwm])*)$`)
+var daystrRe = regexp.MustCompile(`^(\d{4})-(\d{2})-(\d{2})$`)
+
 func UpdateCurrentActivity(ctx context.Context, update ActivityUpdate) error {
 	now := time.Now()
 	dayStr := GetCurDayStr()
diff --git a/wavesrv/pkg/telemetry/telemetry_test.go b/wavesrv/pkg/telemetry/telemetry_test.go
new file mode 100644
index 000000000..875f834e5
--- /dev/null
+++ b/wavesrv/pkg/telemetry/telemetry_test.go
@@ -0,0 +1,41 @@
+// Copyright 2024, Command Line Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package telemetry
+
+import (
+	"testing"
+	"time"
+)
+
+func testCustomDaystr(t *testing.T, customDayStr string, expectedDayStr string, shouldErr bool) {
+	rtn, err := GetCustomDayStr(customDayStr)
+	if err != nil {
+		if !shouldErr {
+			t.Errorf("unexpected error: %v", err)
+		}
+	} else {
+		if rtn != expectedDayStr {
+			t.Errorf("for %q expected %q, got %q", customDayStr, expectedDayStr, rtn)
+		}
+	}
+}
+
+func TestDaystrCustom(t *testing.T) {
+	now := time.Now()
+	bom := now.AddDate(0, 0, -now.Day()+1)
+	testCustomDaystr(t, "today", GetCurDayStr(), false)
+	testCustomDaystr(t, "yesterday", GetRelDayStr(-1), false)
+	testCustomDaystr(t, "bom", bom.Format("2006-01-02"), false)
+	bow := now.AddDate(0, 0, -int(now.Weekday()))
+	testCustomDaystr(t, "bow", bow.Format("2006-01-02"), false)
+	testCustomDaystr(t, "today-1d", GetRelDayStr(-1), false)
+	testCustomDaystr(t, "today+1d", GetRelDayStr(1), false)
+	testCustomDaystr(t, "today-1w", GetRelDayStr(-7), false)
+	day1 := bom.AddDate(0, 1, -1)
+	testCustomDaystr(t, "bom+1m-1d", day1.Format("2006-01-02"), false)
+	testCustomDaystr(t, "foo", "", true)
+	testCustomDaystr(t, "2000-1-1", "", true)
+	testCustomDaystr(t, "2024-01-01+1w", "2024-01-08", false)
+	testCustomDaystr(t, "2024-01-01+1m+1w-1d", "2024-02-07", false)
+}