onboard/app/Services/DateRangeService.php

<?php

namespace App\Services;

use Illuminate\Support\Carbon;

class DateRangeService
{
    public function getDateRangeForUser($user, $startAt = null, $endAt = null): array
    {
        if ($startAt && $endAt) {
            return $this->getCustomDateRange($startAt, $endAt, $user);
        }

        return $this->getDefaultDateRange($user);
    }

    public function isRangeOneDay($startAt = null, $endAt = null): bool
    {
        if (!$startAt || !$endAt) return false;

        $startDate = $this->parseDate($startAt);
        $endDate = $this->parseDate($endAt);

        if ($startDate->diffInDays($endDate) === 1.0) return true;

        return false;
    }

    private function getCustomDateRange($startAt, $endAt, $user): array
    {
        $startDate = $this->parseDate($startAt);
        $endDate = $this->parseDate($endAt);

        if ($startDate->isSameDay($endDate)) {
            $startDate = $startDate->subDay()->setTime(6, 0);
            $endDate = $endDate->setTime(6, 0);
        } else {
            $startDate = $startDate->setTime(6, 0);
            $endDate = $endDate->setTime(6, 0);
        }

        return [
            $startDate->format('Y-m-d H:i:s'),
            $endDate->format('Y-m-d H:i:s')
        ];
    }

    private function getDefaultDateRange($user): array
    {
        $startDate = Carbon::now('Asia/Yakutsk')
            ->subDay()
            ->setTime(6, 0);

        $endDate = Carbon::now('Asia/Yakutsk')
            ->setTime(6, 0);

        return [
            $startDate->format('Y-m-d H:i:s'),
            $endDate->format('Y-m-d H:i:s')
        ];
    }

    public function parseDate($dateInput): Carbon
    {
        if (is_numeric($dateInput)) {
            return Carbon::createFromTimestampMs($dateInput)
                ->setTimezone('Asia/Yakutsk');
        }

        return Carbon::parse($dateInput, 'Asia/Yakutsk');
    }
}